Manual Wellsite Geology
This document was uploaded by user and they confirmed that they have the permission to share it. If you are author or own the copyright of this book, please report to us by using this DMCA report form. Report DMCA
Overview
Download & View Manual Wellsite Geology as PDF for free.
More details
- Words: 24,681
- Pages: 75
Loading documents preview...
Manual Wellsite Geology
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 1 of 75
Title:
Manual Wellsite Geology
Document no. :
Contract no.:
Classification: Internal Expiry date: 2011-02-04 Distribution date:
Project:
Distribution: Corporate Statoil Status Final Rev. no.:
Copy no.:
Author(s)/Source(s): Geo Operations
Subjects:
Remarks: Valid from:
Updated:
Responsible publisher:
Authority to approve deviations:
Techn. responsible (Organisation unit):
Techn. responsible (Name):
Date/Signature:
Responsible (Organisation unit):
Responsible (Name):
Date/Signature:
Recommended (Organisation unit):
Recommended (Name):
Date/Signature:
Approved by (Organisation unit):
Approved by (Name):
Date/Signature:
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 2 of 75
Table of contents
1
Objective............................................................................................................................................... 8
2
2 Data handling and Reporting........................................................................................................... 9
2.1
Introduction............................................................................................................................................ 9
2.2
Data from service companies................................................................................................................. 9
2.2.1
Drilling parameters................................................................................................................................. 9
2.2.2
Mud logs............................................................................................................................................... 10
2.2.3
MWD/LWD data................................................................................................................................... 10
2.2.4
Wireline................................................................................................................................................ 10
2.3
Statoil descriptions and plot/presentations........................................................................................... 10
2.3.1
Lithology Descriptions.......................................................................................................................... 10
2.3.1.1
Summary of Lithology Descriptions...................................................................................................... 11
2.3.2
Well Site Sample Descriptions............................................................................................................. 11
2.3.3
Core Description................................................................................................................................... 11
2.3.4
Sidewall Core Description.................................................................................................................... 11
2.3.5
Wellsite Geology responsibility for making the Completion Log...........................................................11
2.3.6
Pore Pressure and drilling parameters................................................................................................. 12
2.3.7
Risk Log/Trip log.................................................................................................................................. 12
2.3.8
Cross Section....................................................................................................................................... 12
2.4
Statoil Reports...................................................................................................................................... 13
2.4.1
Wellsite Geology Daily DBR reporting requirements............................................................................13
2.4.2
Partner Report...................................................................................................................................... 13
2.4.3
Pore Pressure Report........................................................................................................................... 13
2.4.4
NPD Report/Shallow Gas Report......................................................................................................... 13
2.4.5
Section Report...................................................................................................................................... 14
2.4.6
Detailed logging operation report......................................................................................................... 14
2.4.7
Experience report................................................................................................................................. 14
2.4.8
Input to Final Well Report..................................................................................................................... 14
2.4.9
Evaluation of service companies.......................................................................................................... 14
2.5
Office routines...................................................................................................................................... 15
2.5.1
Introduction/Responsibility................................................................................................................... 15
2.5.2
Daily meetings/Telephone meetings.................................................................................................... 15
2.5.3
Diary..................................................................................................................................................... 15
2.5.4
Manifest................................................................................................................................................ 16
2.5.5
Well archive.......................................................................................................................................... 16
2.5.6
Rig library............................................................................................................................................. 16
2.5.7
Inventory list......................................................................................................................................... 17
2.6
Security routines................................................................................................................................... 17
2.6.1
Geologist’s office.................................................................................................................................. 17
2.6.2
PC – Data equipment........................................................................................................................... 17
2.6.3
Sharing of information.......................................................................................................................... 18
2.6.4
Shipment.............................................................................................................................................. 18
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 3 of 75
2.6.5
Removal of data................................................................................................................................... 18
2.6.6
Samples............................................................................................................................................... 18
2.7
Training of Well Site geologists............................................................................................................ 19
3
Geological Sampling.......................................................................................................................... 20
3.1
Introduction.......................................................................................................................................... 20
3.2
Sample programme.............................................................................................................................. 20
3.2.1
Cuttings samples (drill cuttings)............................................................................................................ 20
3.3
Sample catching (drill cuttings)............................................................................................................. 22
3.4
Sample handling/packing..................................................................................................................... 22
3.4.1
Wet samples........................................................................................................................................ 22
3.4.2
Dry samples......................................................................................................................................... 23
3.4.3
Geochemical samples.......................................................................................................................... 23
3.4.4
Mud samples........................................................................................................................................ 23
3.5
Sample shipments................................................................................................................................ 23
3.6
Material Safety Data Sheet.................................................................................................................. 24
3.7
Sample preparation.............................................................................................................................. 24
3.7.1
Water based mud................................................................................................................................. 24
3.7.2
Oil based mud...................................................................................................................................... 25
4
Pore Pressure..................................................................................................................................... 26
4.1
Introduction.......................................................................................................................................... 26
4.2
Responsibilities related to pore pressure work.....................................................................................26
4.3
Pore pressure work.............................................................................................................................. 26
4.3.1
Methods and terminology..................................................................................................................... 26
4.3.2
Pore pressure calculation..................................................................................................................... 26
5
Geohazards......................................................................................................................................... 27
5.1
Shallow gas.......................................................................................................................................... 27
5.1.1
Introduction.......................................................................................................................................... 27
5.1.2
Wellsite Geology Requirements concerning Geohazards....................................................................27
5.2
Other shallow hazards.......................................................................................................................... 28
6
Directional drilling and geosteering................................................................................................. 29
6.1
Directional drilling................................................................................................................................. 29
6.2
Geosteering.......................................................................................................................................... 29
7
Mud logging........................................................................................................................................ 30
7.1.1
Introduction.......................................................................................................................................... 30
7.1.2
Equipment............................................................................................................................................ 30
7.1.3
Wellsite Geology responsibilities concerning Mud Logging quality control...........................................30
7.1.4
Products from Mudlogging Company................................................................................................... 30
8
MWD/LWD........................................................................................................................................... 32
8.1
Introduction.......................................................................................................................................... 32
8.2
Wellsite Geology Requirements concerning MWD/LWD logging.........................................................32
8.3
Methods used by Wellsite Geologist for check of MWD/LWD operation..............................................33
8.3.1
Well site check prior to logging............................................................................................................. 33
8.3.2
Check list while logging........................................................................................................................ 33
8.3.3
Checks after logging............................................................................................................................. 34
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 4 of 75
9
Wireline Logging................................................................................................................................ 35
9.1
Electrical Wireline logging.................................................................................................................... 35
9.1.1
Introduction.......................................................................................................................................... 35
9.1.2
Responsibilities.................................................................................................................................... 35
9.1.3
Checks prior to logging......................................................................................................................... 35
9.1.4
Pre-job planning meeting..................................................................................................................... 36
9.1.5
Supervision of logging operation.......................................................................................................... 37
9.1.6
Real time Quality control...................................................................................................................... 37
9.1.7
Checks while logging............................................................................................................................ 38
9.1.8
Checks after Logging........................................................................................................................... 39
9.1.9
Log Headings....................................................................................................................................... 39
9.1.10
Log Numbering..................................................................................................................................... 39
9.1.11
Logging Service Bills & Invoices........................................................................................................... 40
9.1.12
Reporting Procedures (Logging Report)............................................................................................... 40
9.2
Borehole Seismic (VSP)....................................................................................................................... 40
9.2.1
Introduction.......................................................................................................................................... 40
9.2.2
Responsibilities.................................................................................................................................... 41
9.2.3
Planning............................................................................................................................................... 41
9.2.4
Before the survey (Before logging operation).......................................................................................42
9.2.5
During the survey (The logging operation)........................................................................................... 42
9.2.6
After the survey (logging operation) - VSP data from the rig................................................................43
10
Coring.................................................................................................................................................. 44
10.1
Introduction.......................................................................................................................................... 44
10.2
The Well Site Geologist's responsibility concerning coring operation...................................................44
10.3
Methods used by Wellsite Geologist during coring operation...............................................................45
10.3.1
Coring programme............................................................................................................................... 45
10.3.2
Equipment for core handling................................................................................................................ 45
10.3.3
Coring point decision............................................................................................................................ 46
10.3.4
Coring operations................................................................................................................................. 46
10.3.5
Tripping speeds.................................................................................................................................... 46
10.3.6
Oriented cores...................................................................................................................................... 47
10.3.7
Handling of cores in the inner - barrel.................................................................................................. 47
10.3.8
Core handling on the drill floor............................................................................................................. 48
10.3.9
Marking................................................................................................................................................ 48
10.3.10 Core Gamma........................................................................................................................................ 49 10.3.11 Core cutting.......................................................................................................................................... 49 10.3.12 Sampling and core description............................................................................................................. 49 10.3.13 Packing of cores................................................................................................................................... 49 10.3.14 Shipment of cores................................................................................................................................ 50 10.4
Gel filled inner-barrels.......................................................................................................................... 50
10.5
Handling of unconsolidated core material............................................................................................ 51
10.6
Special analyses, sealed core ("seal peal").......................................................................................... 51
11
Sidewall coring................................................................................................................................... 52
11.1
Introduction.......................................................................................................................................... 52
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 5 of 75
11.2
Objectives............................................................................................................................................ 52
11.2.1
Wellsite Geology procecures for depth control during sidewall coring..................................................52
11.2.2
Depths for sidewall cores..................................................................................................................... 52
11.3
Operational routines............................................................................................................................. 53
11.4
Use of sidewall cores........................................................................................................................... 53
11.4.1
Geochemistry....................................................................................................................................... 53
11.4.2
Biostratigraphy..................................................................................................................................... 53
11.4.3
Lithology............................................................................................................................................... 53
11.5
Sidewall Core Equipment..................................................................................................................... 53
11.5.1
Reporting.............................................................................................................................................. 53
11.6
Description........................................................................................................................................... 54
11.7
Packing, marking and shipment........................................................................................................... 54
12
Other services.................................................................................................................................... 56
12.1
Introduction.......................................................................................................................................... 56
12.2
Wellsite Geology Requirements concerning other services.................................................................56
12.3
Forms for reporting............................................................................................................................... 57
App A
Lithological Description.................................................................................................................... 58
A.1
Introduction.......................................................................................................................................... 58
A.2
Procedure for rock description.............................................................................................................. 58
A.2.1
Rock names......................................................................................................................................... 59
A.2.2
Modified rock names............................................................................................................................ 60
A.2.3
Colour................................................................................................................................................... 61
A.2.4
Dominant Mineralogy........................................................................................................................... 61
A.2.5
Texture................................................................................................................................................. 61
A.2.5.1
Grain-/Crystal size................................................................................................................................ 61
A.2.5.2
Physical Texture................................................................................................................................... 62
A.2.5.3
Grain - /crystal shape........................................................................................................................... 62
A.2.6
Sorting.................................................................................................................................................. 62
A.2.7
Matrix................................................................................................................................................... 62
A.2.8
Cementing............................................................................................................................................ 63
A.2.9
Hardness.............................................................................................................................................. 65
A.2.10
Cleavage.............................................................................................................................................. 65
A.2.11
Structures............................................................................................................................................. 65
A.2.12
Other components................................................................................................................................ 66
A.2.13
Other characteristics............................................................................................................................ 66
A.2.14
Porosity and permeability..................................................................................................................... 66
A.3
Percentage........................................................................................................................................... 66
A.4
Other relevant advice........................................................................................................................... 70
App B
Wellsite Geology responsibilities concerning Hydrocarbon Shows.............................................71
B.1
Registration of hydrocarbons............................................................................................................... 71
B.2
Gas readings........................................................................................................................................ 71
B.2.1
Ditch gas.............................................................................................................................................. 71
B.2.2
Cuttings gas......................................................................................................................................... 73
B.2.3
Gas Ratio Analysis............................................................................................................................... 73
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 6 of 75
B.2.4
Oil in the mud....................................................................................................................................... 73
B.3
Shows descriptions.............................................................................................................................. 73
B.3.1
Hydrocarbon odour............................................................................................................................... 73
B.3.2
Oil stain................................................................................................................................................ 74
B.3.3
Natural fluorescence............................................................................................................................ 74
B.3.4
Cut fluorescence.................................................................................................................................. 75
B.3.5
Residual dissolution(dried)................................................................................................................... 76
B.3.6
Hydrocarbon shows in oil based mud................................................................................................... 77
B.4
Hydrocarbon show evaluation.............................................................................................................. 77
App C
Abbreviations for Lithological Descriptions....................................................................................78
App D
References.......................................................................................................................................... 91
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 7 of 75
1
Objective
This document is a guiding document concerning the tasks, responsibilities and duties for the Well Site Geologist working with exploration- and development wells. The document intends to ensure that: The Well Site Geologist acts in accordance with the prevailing authority regulations and the compulsory documents in Statoil. The requirements of the specific well project/field development are fulfilled. Reporting and communicating is conducted in a uniform, satisfactory and cost effective manner. The Role Description for Wellsite geologists is given in the Well Construction process (see I – xxxxx). The Competance description for the Well Site Geologist is given in K-23275.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 8 of 75
2
2
2.1
Introduction
Data handling and Reporting
This section gives an overview of the reporting routines and the format of standard products that are produced by the well site geologist on Statoil offshore installations. It covers the interaction between the service companies and the well site geologist, and between the well site geologist and the responsible operation geologist onshore. The reporting routines and products / formats described in this section are to be regarded as Statoil standard. General requirements for data acquisition are given in Theme document Geological and petroleum technical data Acquisition.
2.2 2.2.1
Data from service companies Drilling parameters
This is mainly applicable to exploration wells. (this is described in the mudlogging contract and as such not the responsibility of the Well Site Geologist). The drilling parameters shall be transmitted in ASCII- or LAS-format to the operations office onshore on a daily regular basis and else whenever needed. The Well Project might adjust the procedures. Average values for each 1m and 5m should be given for the parameters in the following order: DEPTH : in ‘meters’ both ‘MD’ and ‘TVD’ with reference to ‘RKB’ ROP : the rate of penetration presented in ‘meters per hour’ WOB : the weight on bit presented in ‘tons’ RPM : presented in revolutions per minute TORQ : the torque presented in ‘Newton meter’ SPP : the stand pipe pressure presented in ‘bar’ FLOW OUT : the mudflow out presented in ‘litres per minute’ TEMP OUT : the temperature out presented in ‘degrees C’ MW OUT : mud weight out presented in ‘gram per cubic centimetre’ ECD : equivalent circulation density presented in ‘gram per cubic centimetre’ Dxc : corrected drilling exponent TOT GAS : total gas presented in percent C1-5 : gas chromatograph readings for the gases C1-5 presented in ‘parts per million’
2.2.2
Mud logs
Mud logs containing drilling parameters and gas information (“Formation Evaluation Log”) should be transmitted after each hole section, or when requested. The log should be transferred to *.pdf or *.pds format before any transmission.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 9 of 75
2.2.3
MWD/LWD data
The MWD/LWD data shall be transmitted, both as a log and as a digital file to the operations office onshore on a daily, regular basis and else whenever needed. The Well Project might adjust the procedures. The normal procedures are described below.
the real time log shall be presented preferably in either *.pdf, *.pds formats which can reproduce the logs in correct scale by using available viewer-programmes . the digital format should be either in ASCII or in LAS format. The data shall be presented with 15cm increments. the MWD/LWD memory log and digital data shall be sent to the Operations Geologist when available, or loaded on to the well project team site.
2.2.4
Wireline
If no Petroleum Engineer is onsite for the logging job, the well site geologist is responsible for the electric logging operation and data quality. It is important to assure that:
Digital log data in ASCII- or LAS-format of wireline data shall be transmitted to the Operations Geologist and the Petroleum Engineer/Project Petrophysicist as soon as possible. When acquiring pressure data, these should be recorded on a spreadsheet, plotted graphically to verify the validity of the readings, and transmitted to the Petroleum engineer / Operations Geologist. Logging reports should be generated during the logging operations and forwarded to the Petroleum engineer / Operations Geologist or posted on the well project team site.
2.3 2.3.1
Statoil descriptions and plot/presentations Lithology Descriptions
Cuttings and core descriptions shall follow the standards given in Appendix A and B. The abbreviations shall follow the AAPG standard reproduced in Appendix C.
2.3.1.1
Summary of Lithology Descriptions
If the Winlog programme is used for log preparation the summary of lithological descriptions will be put into Winlog directly. If not, a special spreadsheet for the descriptions shall be prepared. The lithology description should be a summary of the sample-/core descriptions covering a defined section or a formation/group. The descriptions should be with abbreviations.
2.3.2
Well Site Sample Descriptions
The standard sample description form shall be used and written electronically. When starting a new well, a new description form/file should be used (Link to Statoil’s Wellsite sample description form). Be aware of special procedure for extending this word file, which makes it possible to have different headings on different pages. READ
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 10 of 75
the instruction at bottom of file. After each section the lithological descriptions shall be sent to the operation geologist or uploaded to the teamsite.
2.3.3
Core Description
The core log in the Winlog programme is used for the presentation of core descriptions. For core chip description the Core chip description form should be used and these descriptions are to be written electronically, Link to core chips description form. It is important to agree on depths of top and bottom of cored interval with the drilling supervisor. 2.3.4
Sidewall Core Description
The standard sidewall core description form will be used. The description shall start with the uppermost core and end with the lowermost core. Further details in Chapter 7.7. Link to sidewall core description form.
2.3.5
Wellsite Geology responsibility for making the Completion Log
The Completion Log shall be prepared in the Winlog application (Statoil’s standard application). Winlog is the log drawing software that shall be used by Statoil for preparation of completion-, core-, and trip risk logs. It can also be used to generate geological prognoses and summaries for well Programmes and final well reports. Access to the software is acquired via Access IT. The installation includes necessary font files, log patterns, and log templates. It is recommended to bookmark the following link to the Statoil Winlog user guide and get familiar with the guide before start using Winlog.
Statoil Winlog User Guide The LWD logs and/or the wireline logs, together with the sample and core descriptions, will be the primary sources for geological interpretation. The Completion Log should be updated as much as possible preferable with the last versions of wireline and/or MWD/LWD memory logs. Additional data as surveys, ROP, Gas readings, bit information and mud data shall be used. The lithology descriptions shall be with abbreviations. It is recommended that descriptions are organized with depth intervals spesifications as e.g.: 1830 – 1890m TVD: Interbedded sandstone and claystones with limestone stringers. Details about individual lithology types are then given according to depths of occurrence. Sst: clr transl Qtz ……
2.3.6
Pore Pressure and drilling parameters
The parameter plot shall be prepared by the Well Site Geologist and should be kept updated during the operations. The plot must always be easily be available for the Well Site Geologist if the mud loggers do the plotting. The Statoil standard drilling parameters plot contains: ROP, WOB, RPM, Dxc, Tot GAS, TEMP and MW OUT plotted every 5m. Shale density and calcimetry plotted on request
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 11 of 75
the main lithology and the stratigraphy shall be included connection gas, trip gas and gas peaks should be noted on the gas curve (Tot GAS) comments concerning the well head, casings, mud weight, hole problems and other relevant items should be included under "Remarks" sonic data shall be plotted when available pore pressure results/calculations, at interesting levels, should be noted with depth and together with the Dxc (actual value), Dxn (normal/trend line value) and OBG (overburden) used for the pressure calculation. Similar calculation is made by use of resistivity and sonic logs.
For further details concerning pore pressure and Predict/software see Link to Theme document pore pressure. 2.3.7
Risk Log/Trip log
Before tripping out of hole, the Well Site geologist might be asked to make a risk log for the drilling crew. The log is made by the Winlog risk log template. This log should contain information concerning hole condition and hole stability, such as information about sand intervals, coal stringers, limestone/dolomite stringers, swelling clay, inclination etc. 2.3.8
Cross Section
It might be useful to have a geological cross section with well data in order to be able to correlate the well data with the reference wells. This is mainly applicable to production wells and made onshore before operation starts. Necessary files and information will be supplied by the Operations Geologist. 2.4 2.4.1
Statoil Reports Wellsite Geology Daily DBR reporting requirements
The DBR (daily drilling report) shall be filled in every morning before 07:00 and shall cover the period from 00:00 a.m the previous day until 24:00 a.m. on the reporting day. The Well Site geologist is responsible for all information in part 7. Geology/ Pressure Data and part 14. Logging, in addition to input to the geological section report, part 1. All depths and all drilling/engineering data reported must be in agreement with similar data reported by the drilling department. In part 7. Geology/ Pressure Data the General lithology shall be written in full text and the lithology properties shall be written in abbreviations. Description of the formations shall be written into the part Preliminary zonation. In DBR, part 14.0 Logging short remarks can be added for each logging run separately. Further remarks can be added in 14.4 Logging remarks. Be aware that all information from part 14. Logging will be included in the section reports, while information from Geology remarks in part 7. Geology/ Pressure Data will not be included in the section reports. Detail about the DBR reporting system are found in the Well Site Geology Course Documentation
2.4.2
Partner Report
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 12 of 75
The daily geological morning report (applicable for exploration wells) is a part of the DBR Partner report and should be updated before 07:00 a.m. and quality controlled by the Operations Geologist prior to distribution.
2.4.3
Pore Pressure Report
The pore pressure report is a part of the daily DBR and the Section report, and shall contain the following information: Statoil's pore pressure estimation/calculation. Methods used for calculation of the pore pressure, and which data it is based upon. All pressure related problems in the well.
2.4.4
NPD Report/Shallow Gas Report
The NPD Standard sheet for reporting shallow gas are to be completed after drilling the top hole sections (including 26”), and then sent to Operations Geologists.
2.4.5
Section Report
A Section report shall be finalized for each hole section. The report is made in the DBR report system and contains information both from the geological summary in part 1 and from the daily reporting in DBR. New input shall be written into part 1. Daily Status – Section – Geological summary with relevant data regarding operations and data acquisition. In addition the description of formations has to be checked and updated in part 7. Geology/ Pressure Data – Preliminary Zonation. The logging information will also have to be checked and updated in Part 14 Logging. The purpose of the report is to register experiences and to give the first sketch of the Final Well Report.
2.4.6
Detailed logging operation report
This report shall be written in a word document for all wireline logging operation. Link: Theme Document Electrical Wireline logging.
2.4.7
Experience report
Experience report in DBR shall be written whenever relevant. This could be either positive or negative experiences, if necessary the report can be written in co-operation with drilling supervisor or drilling engineer.
2.4.8
Input to Final Well Report
In some cases the Well Site geologist might be asked to give input to the Final Well Report. The necessary files and information will then be supplied by the operation geologist.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 13 of 75
2.4.9
Evaluation of service companies
It is the responsibility of the Well Site Geologist to give input to the evaluation of the service companies on site. For mudlogging companies and the MWD/LWD service, an evaluation form is to be completed for every section. For other companies this form is to be completed for every job; example wireline, coring, core handling etc. Experiences are to be written into the form before leaving the rig, even if the section or job is not finished. The completed form should be sent to the Operations Geologists. Link to the evaluation form. Evaluation of the service representative’s performance should be included in this report and not in the DBR. The Well Site Geologist has a special responsibility to ensure quality and to report failures connected to mud logging, LWD, wireline logging and other geologically relevant items. Additional RUH or non-conformance reports shall be filled out for certain failures as: equipment failure unsuccessful logging - ("misrun") operator failure causing lost rig time For further details concerning the different services/companies and their deliveries, see the relevant sections in this document and other relevant mandatory and guiding documents.
2.5 2.5.1
Office routines Introduction/Responsibility
The Well Site Geologist has the responsibility to keep the geologist's rig office at a security standard according to the routines given below. He/she is also responsible for ordering the necessary office equipments and for keeping the well archive on the rig in a complete and updated state. Confidential geological information shall only be available to other than the geologists on a "need to know" basis.
2.5.2
Daily meetings/Telephone meetings
All rigs and platforms have regular meetings regarding the on-going operation, administrated by the Drilling Supervisor, both in the morning and in the evening for both shifts. In addition there are regular telephone meetings in the morning and at times also in the afternoon with the Well Project onshore. The timing for the different meetings may vary from rig/platform and project. The Wellsite Geologist is obliged to: Attend the morning/evening meeting on the site (rig/platform). Attend the morning/afternoon telephone meetings between the Drilling Supervisor on the rig and the Drilling Superintendent onshore. Have telephone correspondence with the Operations Geologist according to agreement Inform the Operations Geologist or duty Operations Geologist as soon as possible about all important issues, such as major deviation from geological and pore pressure prognosis, the first indications of hydrocarbons, results from coring and when the final TD is reached. Contact the Operations Geologist or duty Operations Geologist at every occasion of non-conformance related to the Well Programme and/or other mandatory documents for the Well Project.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 14 of 75
2.5.3
Diary
It is recommended to use a diary. The purpose of the diary is to ascertain that all messages, information and other communication with the operations office onshore and the service companies, are registered and thereby also available for the other geologist on the work schedule. The intention is to have the diary as a supplement to the handover between the shifts. The diary is supposed to be updated when needed, and it can adapt to the daily drilling reporting time, which following the working shifts on the rig/platform. The diary can either be electronically stored and/or as a bound book. The diary will primarily contain the following information: a brief operational status pore pressure (see mandatory and guiding documents concerning pore pressure) All correspondence between the Well Site Geologist and the Operations or Duty Geologist. Actual shipping times, correspondence with other rig personnel, orderings etc.
2.5.4
Manifest
All manifests are to be mailed to the operation geologist when samples are sent from the rig. The following information shall be included: sample type, depth intervals, mud type and mud company, time and way of dispatch, flight number or ship name, cargo number if used, container number, receivers address and contact person.
2.5.5
Well archive
On some production platforms there is a well archive with geological data. The well archive on the rig/ platform shall be updated after each well. It could include copies of all relevant reports, forms and log, as listed below: Drilling programme. Technical background documentation for the actual well (DOR, DOP, etc.) Site Survey Report Dispatch notes and possible other manifests Mud logging company's inventory list Mud logs LWD logs Wireline logs
2.5.6
Rig library
All of the mandatory and guiding documents necessary for the Well Site Geologist are available as digital document in APOS. Other documents for exploration and development wells might be available: Completion logs for reference wells OD Bulletin’s nr. 3, 4 and 5 Final Well Reports for the reference wells and other relevant data from neighbouring wells; such as section reports, electrical logs, LWD logs, mud logs and parameter plots. Statoil pore pressure course. (Rafdal 1994) Mud Logging Handbook (Whittaker) Statoil Wireline Formation Evaluation Operation Procedures, Electrical Wireline Best Practice Document
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 15 of 75
Manual for Core Handling. VSP acquisitions, processing and sonic log calibration. Schlumberger/Atlas wireline logging manuals, calibration books etc. dictionaries: English-Norwegian/Norwegian-English Technical dictionary Glossary of Geology, (Bates & Jackson)
And in addition the following documents may be useful: Log Data Acquisition and Quality Control (Theys) A new method for pore pressure evaluation by using DC-exponent and Sonic logs (J. Skagen) Internal publications/notes concerning the actual area 2.5.7
Inventory list
The geologist's office shall be furnished or have access to the following equipment: PC, monitor, printer, scanner, etc. paper shredder Communication equipment Internal and external telephone lines, fax and a PC linked to the Statoil network (Daily Drilling Report and other relevant databases).
2.6 2.6.1
Security routines Geologist’s office
The geologist's office shall at any time be kept tidy. When the Well Site Geologist leaves the office for shorter or longer periods, no restricted/confidential material shall be left at the desk, and the well file shall be copied to G: disk, and deleted from the PC. Some wells will, by the customer (the licences), be defined as "tight wells". While drilling such wells special security routines, defined by the Well Project/the Operations Geologist, will be followed. Documents that contain confidential information shall be sent onshore to be if this for some reason cannot be done on the rig. All documents shall be locked up and the PC shall also be locked if/when either Statoil's geologist or petroleum/testing engineers are not on board the rig. 2.6.2
PC – Data equipment
Only Statoil employees and personnel approved by Statoil are allowed to use Statoil's data equipment. Information of the personal ID-code and password(s) shall not be shared with other persons. The data lock shall be active as long as the office is unmanned, in order to prevent that non-Statoil personnel log on to the data equipment. It is not allowed to install copies of data programmes which is not given a data virus control
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 16 of 75
2.6.3
Sharing of information
The service companies are entitled to all the information needed in their daily work, however nothing more than that. This usually means parts of the Drilling Programme. The service companies are not allowed to share information with other service companies without permission from the Well Site Geologist. The service companies have to be informed of this practice, for instance by the Well Site Geologist or the Statoil Drilling Supervisor.
2.6.4
Shipment
Shipments of data, such as logs and reports are normally done by e-mail, memory sticks/DVD/CD, etc., and non electronic shipment of data shall only be carried out in one of the following two ways: In a locked Statoil mail bag, with helicopter/aeroplane. Hand carried by Statoil personnel, or by personnel approved by Statoil if they are going directly to the Operations office. A dispatch note shall be attached to all shipments
2.6.5
Removal of data
The Well Site Geologist has to ensure that all written documentation that have been distributed to rig personnel, are returned and filed or destroyed, at the latest when the well is finished. In situations where another operator shall use the rig, all Statoil equipment and documentation have to be removed from the geologist’s office and shipped onshore.
2.6.6
Samples
Packing, marking and shipment of samples should be carried out according to the given routines (see Chapters 4.4 and 4.5). A set of dry samples shall be kept on the rig until the well is finished. 2.7
Training of Well Site geologists
The Well Site geologist is required to actively supervise and train the trainee Well Site geologist. Link to The Geology Qualification scheme should be used for this purpose
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 17 of 75
3
Geological Sampling
3.1
Introduction
The Well Site Geologist is responsible for ensuring that sufficient material are collected according to the Well Programme, and he/she shall supervise the sampling and ensure required labelling. Authority requirements shall also be met, reference to the documents "Acts and regulations", edited by NPD (available on http://npd.no), and likewise all Statoil requirements shall be fulfilled. 3.2
Sample programme
A detailed sample programme is included in the Well Programme, and it is mandatory to comply with this. 3.2.1
Cuttings samples (drill cuttings)
The mud logging company is responsible for the catching, preparation and shipment of the samples. It is the Well Site Geologist’s responsibility to ensure that this is done according to Statoil’s requirements and as specified in the Well Programme. See Chapter 3 $9 in Link to NPD’s Ressursforskriften. 4.2.1.1 Wet samples
To be packed unwashed, usually with 10m or 3m intervals. The samples are normally collected in 5 litres buckets and processed onshore. If separate samples are collected, the samples shall contain minimum 500 g, and the NPD sample shall contain minimum 1 kg. If minor amounts of cuttings are coming over the shakers, the NPD should have 50% of it. In exploration wells sampling shall commence as soon as returns have been established, according to the programme. In development wells the sample programme might be reduced after samples have been taken from a representative selection of the wells. Normally only wet samples from the reservoir and source rocks will be collected. The intervals between the samples shall not exceed 10 m. In long hole horizontal sections with layer parallel drilling, sampling interval of 20m might be sufficient. When drilling exploration wells in potentially hydrocarbon bearing layers, the samples should be collected with intervals not exceeding 3m if conventional cores are not taken. The samples should be as representative for the interval sampled as possible and standard procedures for handling of the samples should be followed. Cuttings samples should also be collected during coring if possible, in order to have back-up material in case of lost core(s).
4.2.1.2 Dried samples
Washed and dried, normally 100 g, and minimum 10 - 20 g. One set of samples shall be prepared and stored on the rig until the well is completed. Dried samples can also be prepared in the laboratory onshore
4.2.1.3 Mud samples
Mud samples (1 litre) will normally be collected when the mud characteristics are changed and/or when introducing new chemicals/additives in the mud
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 18 of 75
In exploration wells mud samples will be collected when drilling through hydrocarbon bearing formations and into the water zone; according to data acquisition programme. Irrespective of sample intervals, mud samples shall be collected if traces of oil are registered in the mud. It may be wise to try to "skim" the oil film in order to get a sample as rich as possible for analysis. These samples shall immediately be shipped to the relevant laboratory.
4.2.1.4 Geochemical samples Samples for geochemical analysis shall be sealed, unwashed, in tin cans (or suitable plastic bottles) after adding bactericide; according to data acquisition. These samples are usually "composite samples", a part of the sample is collected together with each wet sample. 4.2.1.5 Ditch Gas samples Drill gas might be collected according to data acquisition programme. This might be done in gas bags or iso-tubes. 4.2.1.5 Sidewall Cores A detailed description of the Sidewall coring operation is found in chapter 12. 4.2.1.6 Core Sample A detailed description of the coring operation is found in chapter 11. 4.2.1.7 Fluid an Gas Sample A detailed description of the Fluid Sampling operation is found in chapter 10 and Link: Theme Document Electrical Wireline logging. 4.2.1.8 Other Sample Extra Cement and mud samples are frequently collected by the representative contractors for analysis. If not stated in the Well Programme it is normally not a Well Site Geologists responsibility. However, if alterations are made which has implications to any aspects of the Formation Evaluation it must be detected and reported. Likewise it is important that the Well Site Geologist consult the Wireline Logging Programme/Coring Programme etc. for proactive actions, like adding of Tracers to mud, verifying ditch magnets in flow line and the collection procedure for weighing the magnetic steel, if a CMR log is requested.
3.3
Sample catching (drill cuttings)
The correct "lag time" is of great importance for the sample quality and the depth control. The Well Site Geologist should ascertain that the lag time is checked on a regular basis. The following methods can be used for calculating the "lag time": Distinct marker beds identified by drilling parameters, or MWD log responses. by registration/correlation of gas peaks versus increased drilling speed ("drill break") by registration of trip gas or connection gas. In this case one has to be quite certain that the gas comes from the TD and not from a shallower level. carbide test (to be performed by the mud logging engineers). Due to a certain risk of plugging, the use of carbide should always be given a thorough consideration. Only soluble packing’s should be used.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 19 of 75
The samples are to be collected from the sample board placed underneath the shale shaker. The samples should be collected from the entire sampling interval, it is therefore important to check that the sample board is cleaned after the collection of each sample. It is the responsibility for the Well Site Geologist to establish proper routines to be followed by the sample catchers and the drilling crew, in order to prevent that the samples are washed away. The shale shaker screens should be as small scaled as possible, but big enough to enable additives to the mud and the mud through. In situations with minor amounts of return over the shale shaker or when drilling in unconsolidated sand, the samples must be collected from the "desander/desilter" ("lag time" will not be accurate). If samples are caught from other places than the shale shaker it has to be noted in the description form under “remarks”. It is a good practice to collect samples regularly from the "desander/desilter", in order to get an impression of the "normal amount" of fine sand/barite. Fast drilling in the larger hole sections causes the cuttings to build up almost instantaneously on the board after cleaning out the cuttings. Therefore the interval sampling appears as “spot samples in reality. To avoid this, only a minor portion of the returns could be guided to the board or a sampling bucket. This can in practice be done by mounting a cuttings guide tray with a choke without interference of other actions around the shakers. 3.4
Sample handling/packing
3.4.1
Wet samples
Wet samples shall either be packed in plastic bags and thereafter in cloth bags or plastic coated paper bags, or in 5 litres plastic buckets/tin cans. The bags and buckets/cans shall be marked with the company name, well number and depth/depth interval. The bags shall be placed in standard wooden boxes, on the outside marked with the company name, well number and serial letter and box number (2A, 2B, 2C,...) The depth interval shall be written on the inside of the box. The buckets shall be placed on pallets with suitable frames. Wet samples in boxes which are to be shipped by commercial aircraft (e.g. Series A paleo.) must be Enclosed in a large plastic bag and sealed to prevent leakage in the aircraft. 3.4.2
Dry samples
The dry samples shall be packed in standard paper envelopes and thereafter in cardboard boxes and transported onshore in wooden boxes. The envelopes and the cardboard boxes shall be marked with the company name, well number and depth, the transport boxes shall be marked in the same way as for wet samples.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 20 of 75
3.4.3
Geochemical samples
The samples shall be filled in tin cans; 3/4 should be filled with the sample itself and thereafter the cans should be filled up with drill water and a drop of bactericide. The cans shall be stored and shipped upside down. The sealing of the tin cans have to be checked regularly. Cans with a pressure sealing lid are recommended. In order to prevent damage to the sealing ring upon sealing, it is useful to put a board (wood) on top of the lid and then knock once on the board with the hammer. This results in an even pressure to the entire sealing ring. The cans shall be marked with the company name, well number and depth. The shipment of the cans will be in wooden boxes, marked as described above. 3.4.4
Mud samples
The mud samples should be filled in tin cans or suitable plastic bottles. One reference mud sample will be taken before the drilling operation start. The rest of the mud samples will be taken according to the sampling programme. Marking and shipment will be as for the geochemical samples. 3.5
Sample shipments
All samples shall be transported in containers. The boxes and pallets must be loaded in a stable way and secured by straps and nets. A dispatch note, with well number, sample type(s),depth intervals, mud type and mud company, box number and the amount of boxes, shall be placed in one of the boxes. This specific box has to be marked with "Dispatch note" with the receiver's address and sending it together with the other papers from the rig. The samples shall be shipped onshore to the person/institute responsible for further treatment on a regular basis (for instance weekly or after each hole section). In some situations helicopter transport may be appropriate. The dry samples shall be kept on the rig until the well is finished as a security action. It is the Operations Geologist’s responsibility to forward the samples to the laboratory/storage address. A copy of the dispatch note (Manifest) must be sent to the Operations Geologist.
3.6
Material Safety Data Sheet
To ensure that all involved personnel takes the precautions needed to handle the material in a safe manner, the following routines shall be followed for labeling and transport of geological samples: 1. The mudlogging company shall mark all samples from the rig with HSE information a. Data sheet from the mud engineer shall be available in the mudlogging unit. b. HSE-data sheet, both in Norwegian and English shall be put together with every sample shipment that is sent from the rig, both by helicopter and boat c. The manifest shall give information about sample type, depth intervals, mud type and mud company.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 21 of 75
d. If the mud type has been changed, samples from different sections must be packed in different collies. 2. Reslab will receive the samples from the rig together with HSE data sheet. a. If HSE-data sheet is missing, the sender must be informed immediately. The Statoil Operations Geologist shall also be informed and a synergi report will be written. 3. When Reslab forwards samples to geochemical- or biostrath-laboratories, a copy of all HSE data sheet’s shall be sent together with the samples. The manifest shall contain information about which mud type that has been used in the different intervals sampled. 3.7
Sample preparation
The preparation of the samples for description and storing is very important and the Well Site Geologist shall ascertain that the following standard routines are used. 3.7.1
Water based mud
the sample shall carefully be washed through a 4mm sieve and collected in a 120-micron sieve underneath. In reservoir intervals and in unconsolidated intervals, a 90-micron sieve is to be used (not in top holes) as the lowermost sieve. the water stream shall be kept on a low level, in order to avoid out washing of soft and unconsolidated formations. Due to this risk of out washing, a small amount of unwashed sample shall always be attached for description. At the same time one should be aware that not enough washing will tend to leave a thin film of dried mud around the dried sample. Re-washing in the laboratory may destroy the sample. after being washed a thin layer of cuttings shall be distributed evenly over a suitable board, in order to drain away surplus water. A tag with a notation of the correct depth shall always be attached. dry samples shall be dried slowly with low temperature, normally 40 0C.
3.7.2
Oil based mud
Only the oil component that is already in the mud, the base oil, must be used when washing the samples.
Place the sample in a coarse sieve. Put a fine sieve, 90/120 micron underneath. The sieves should thereafter be lowered in a container with base oil in such a way that all the sample material is covered by oil. Shake well and let the oil drain away. Repeat this procedure 3-5 times. remove the coarse sieve and wash the sample with rig wash or another suitable type of soap in the fine sieve another 1-2 times as described above the sample should now be placed on a sample board, and some of the same oil should be added. Distribute the sample evenly on the board and let it drain. The sample will now be ready for a microscope inspection before doing density measurements, remnants of oil film on the samples have to be removed by using a solution product (the same as being used for "shows" evaluation). The sample should thereafter be air dried before it is dropped in the column for density measurement. the dry sample procedure is the same for oil-based mud as for water-based mud.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 22 of 75
4
Pore Pressure
4.1
Introduction
The Well Site Geologist has a special responsibility connected to the pore pressure surveillance. Close cooperation with the Drilling Supervisor on the rig and the Mud Logging Engineer is needed. In wells with uncertain pore pressure prognosis and in exploration wells, a pore pressure plot shall be generated and kept updated at all times. This is particularly important in HTHP wells and when drilling wells in areas without any reliable background information. Statoil "Pore Pressure Manual" and Statoil "Pore Pressure Course Manual" (Mandatory document for pore pressure work in Statoil), "Link: Theme document pore pressure" describes the procedures to be used. All documents shall be available at well site. 4.2
Responsibilities related to pore pressure work
The main responsibilities for the Well Site Geologist are: estimation of the pore pressure in Statoil operated wells by using available software surveillance, plotting and interpretation of relevant data daily reporting to the Drilling Supervisor of the pore pressure estimate ascertain that only one pore pressure is reported to the operating office onshore, for a given depth updating the journal with the pore pressure value(s) preparation of the pore pressure summary inform the drilling management immediately if changes in the pore pressure and/or deviations from the pore pressure prognosis occur Verify results of FIT, LOT and XLOT For further details reference is made to Chapter 3.3.6 of this document and the mandatory/guiding documents mentioned above. 4.3 4.3.1
Pore pressure work Methods and terminology
The methods and the terminology to be used, and which parameters and logs to be used are described in the above mentioned mandatory/guiding documents. 4.3.2
Pore pressure calculation
Use the pore pressure software that is available on the rig/platform. Reference is made to Chapter 3.3.6 and Link: Theme document for pore pressure.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 23 of 75
5
Geohazards
5.1
Shallow gas
5.1.1
Introduction
Shallow gas is usually defined as non-commercial Hydrocarbon accumulation in younger sediments. Shallow gas typically occurs between approx. 100 meters and down to 1000 meters below seabed. In fairly unconsolidated formation and is characterized by having a high flow potential. Usually the gas occurs in local thin sandstone beds with a thickness of less than 10 meters, but occasionally the gas may occur over a large area (several kilometres in extent). Shallow gas exists all over the Norwegian continental shelf and, world wide, has caused more blowouts and rig losses than any other well control problem. Prior to finalizing the location for a well or platform, a site investigation (Site Survey) will be carried out. This, amongst other things, will be designed to detect and map shallow gas and the full report will be delivered to the NPD (the Norwegian Petroleum Directorate) together with the main drilling programme.
5.1.2
Wellsite Geology Requirements concerning Geohazards
There shall always be a Well site Geologist at the well site when drilling through possible shallow gas zones. The well site geologist shall: Have a thorough knowledge of the site survey report and the Statoil verification of site survey results Have a complete overview of prognosed shallow gas zones from the Drilling programme. Be familiar with analogous problems in neighbouring wells. Know that it is difficult to map shallow gas from seismic data and not trust blindly in the prognosis. Observe closely all possible gas “signals” from the well (ROP, LWD/MWD, ROV, gas problems when hole is tight etc.). Ensure that the rate of penetration is limited to the data acquisition rate of the LWD/MWD equipment can detect formations containing shallow gas. Report immediately to the Drilling Supervisor any indications of shallow gas. Be aware of the swabbing effect when picking up during connections.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 24 of 75
Class
Risk
0
Low risk (Class 0 shall never be given if any doubt whether shallow gas can be excluded)
I
Low/medium risk
II
High risk
III
Very high risk
5.2
Shallow gas assessment Shallow gas is NOT predicted
Indication in well No indication on MWD
Shallow gas w/ normal pressure is predicted or cannot be excluded
How to drill top hole May drill full size hole directly, Evaluate the need for pilot hole: - In a new area - If the area is known to have shallow gas - If drilling from a jack up. Drill pilot hole with sea water. If MWD indicate gas, flow check. Continue drilling.
Questionable/ shallow gas indications on MWD. Well stable with sea water Shallow gas w/ Shallow gas Consider placing casing above. If abnormal pressure is indications on necessary to get surface casing predicted MWD. Well flows deeper, use pilot hole and weighted with sea water. mud (min. 1,10 SG) when entering zone of interest. If MWD indicate gas, flow check. Continue drilling with weighted mud only. Shallow gas w/ Shallow gas abnormal pressure indications on MWD. Gas is blowing uncontrolled
Other shallow hazards
In addition to shallow gas, several other shallow hazards also exist. At the moment there are no formal requirements how these hazard should be treated, but the Well Site geologist should be aware of these. Many of these hazards are related to drilling in deep water (> 1000 m). In certain areas shallow water flow will be a potential problem. The Well Site geologist should be aware of:
Shallow water flow. Weak formation (for example ooze) Boulders/ gravel beds Shallow cemented sand Loose sands
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 25 of 75
6
Directional drilling and geo steering
6.1
Directional drilling
The different companies have different tools for directional drilling. These tools behave different and an experience with the different tools is needed to be able to plan and assist the service company during operation. 6.2
Geosteering
When geosteering a well with aid of real-time LWD logs, it is critical that the real time log quality is sufficient to make correct decisions. If any vital sensors fail during drilling, the Operations Geologist should be contacted and drilling should be stopped until the failure is corrected. Link: Theme document for Geosteering.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 26 of 75
7
Mud logging 7.1.1
Introduction
The Well site Geologist shall ensure a good data quality and that the data acquisition programme is followed. The mud logging service has two main roles during the drilling operations: As a data acquisition service, sampling, and sample handling As a safety service, to record and identify possible risks. 7.1.2
Equipment
The mudlogging equipment is stead in the mudlogging contract. 7.1.3
Wellsite Geology responsibilities concerning Mud Logging quality control
The Well Site Geologist is responsible for the quality control of both the working routines and the acquired data. The Well Site Geologist should: Be acquainted with the different instruments and their way of functioning; ascertain that they always are operational and that calibrations are performed according to the quality control manuals of the mud logging company. Ensure that the calibration of the following instruments are performed at least once a week the total gas detector the chromatograph the H2S detector The calibration of all instruments shall be documented on Statoil request. Check that all sensors are correctly located, and that maintenance and cleaning are done according to schedule. Make sure that all equipment failures are reported on RUH-forms and in DBR. Check that all received data are as correct as possible and that they are ready at the given time limits. Actual data in this respect are: drilling parameters Dxc values, the calculations have to be checked by the start of each hole section the formation evaluation log (mud log), the format has to be discussed with the Operations Geologist when starting the drilling. Check that the sample collection is performed according to the Well Programme and in accordance with Statoil's procedures. Establish a close and continuous co-operation with the mud logging personnel, especially for pore pressure calculations. Provide necessary information to the mud loggers. Ensure that working routines and procedures for the different analyses, such as calcimetry, shale density i.e. are consistent and in accordance with the service company's guidelines. 7.1.4
Products from Mudlogging Company
Each Well project will before spudding of the well, give the project's specific requirements. Statoil will usually require the following logs and other data on a regularly basis (recipients in brackets): "Formation Evaluation Log", digital/paper copy, (Operations Geologist/Well Project and rig archive) "Pressure Evaluation Log", digital/paper copy, (Operations Geologist/Well Project and rig archive) "Digital Drilling Data ", 1 m interval and 5 m interval, (Operations Geologist/Well Project and rig archive), Other logs and extra copies will be made if needed.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 27 of 75
In addition, the mud-logging engineers shall each week prepare an updated inventory list of articles of consumption (bags, boxes etc.).
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 28 of 75
8
MWD/LWD
8.1
Introduction
The purpose of this chapter is to secure a standardized planning, operation and reporting of MWD/LWD operations in Statoil. The Well Site Geologist/ Petrophysicist / Petroleum Engineer is responsible for quality control and interpretation of the LWD logs onsite. He/she is responsible for making sure that the work is performed according to, and also that the data are in accordance with the requirements given in Statoil's mandatory and guiding documents for logging ( Link to Theme document MWD/LWD). There are many reasons for running LWD:
8.2
drilling/geosteering formation evaluation/well correlation optimize the drilling operations shallow gas detection well correlation identifying formations, tops and marker beds/horizons reservoir and hydrocarbon detection casing setting deciding coring points pore pressure evaluation directional measurements measurement of down hole drilling parameters (WOB, RPM and torque), pressure and temperature in the mud column compulsory logging as replacement for wireline logging
Wellsite Geology Requirements concerning MWD/LWD logging
The Well Site Geologist / Petrophysicist/ Petroleum Engineer shall:
Be acquainted with the LWD equipment to be used and its functioning. In co-operation with the drilling management on the rig/platform, make sure that the necessary equipment, including backup equipment, is available on the rig when needed. At all time know the objective(s) for the logging operations and of the priority of the data. When preparing the BHA with the LWD tool included, make sure that the requirements related to the geological data acquisition are attended Be sure that limitations of the LWD equipment (critical RPM, pump rates, pressure drop i.e.) are considered before running the LWD tools in the hole Final logs have to be compared with the raw data and/or the "field copy", since it may happen that anomalous, but correct, readings are edited, for instance low resistivity in pyrite Ensure that all data, both plots and digital data is recorded and reported according to the requirements. Details regard standards for reporting, log presentation etc. are given in Link: Standard Operational Procedures (SOP).
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 29 of 75
8.3
Methods used by Wellsite Geologist for check of MWD/LWD operation
8.3.1
Well site check prior to logging.
Make sure to know the logging programme and its objective.
Discuss the choice of bottom hole assembly and the position of the MWD tool with the Logging Engineer and the Drilling Supervisor to make sure that it agrees with what is required to fulfil the objectives of the run.
Ensure that the tools needed and back-up equipment needed for the job is on board.
Ensure that the Logging Engineer is provided with the following correct data:
Well number, location, water depth and KB elevation. Information on expected bottom hole temperature and pressure. Maximum temperature rating is usually 150°C. Planned TD prior to each run. Make sure that the sampling rate for the tools are known such that the maximum allowed ROP for acquiring a good quality log is not exceeded (usually 3 readings per meter).
Make sure that the Kelly height sensor and signal receiver have been checked out by the engineer.
Make sure that the tool is run in the correct mode (MWD or tool face mode) for the job. 8.3.2
Check list while logging
Make sure that the logs overlap with the previous run. In the case of the need for reaming a section to fulfil this, it has to be discussed with the Operations Geologist. Check log response with previous log runs/reference logs. Make sure that the Logging Engineer routinely measures mud resistivity and temperature out and that correct correction factors for the actual hole size and tool size are being used. Accurate environmental corrections are possible only if the mud data are available. Every time the mud is changed (weight, composition etc.) a new set of mud parameters must be reported. For the GR also mud weight and barite content should be used for correction of the log. Make sure that the maximum allowable ROP is not exceeded. Continuously check log responses and question any unusual responses. Watch the shock counts on the tool if available. If excessive shocks, discuss with the Logging Engineer and recommend corrective actions to the Drilling Supervisor. In the case of a tool/sensor failure, inform the drilling supervisor and the operations geologist. POOH might be necessary.
8.3.3
Checks after logging
If failures during operation check that the tool is visually inspected after operation.
If the tool have to be rerun, consider having it changed out depending on the operating hours
In the case of sections of missing/poor data, reaming and logging of those sections on next run has to be considered.
Ensure that all data is reported according to the Statoil’s requirements
Record MWD temperature and report on daily drilling report.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 30 of 75
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 31 of 75
9
Wireline Logging
9.1
Electrical Wireline logging
9.1.1
Introduction
This chapter is a guideline for well site geologists for supervising and witness electrical wireline logging. For further details see Link: theme document Electrical Wireline Logging. This chapter does not contain the following information:
9.1.2
Details on the operating procedures for electrical wireline logging in general. Details on the quality control requirements for specific log types. Details of the formats and layouts of logs.
Responsibilities
The Well Site Geologist / Petroleum engineer / Petrophysicist have the following responsibilities while logging: 9.1.3
Ensure all safety precautions have been taken Supervise operations Log quality control Supervise well site product delivery & distribution Ensure that reporting and follow up are completed Checks prior to logging
Prior to or during the pre-logging meeting, the Well Site geologist/Petroleum engineer / Petrophysicist should discuss the logging Programme in detail with the Operations Geologist or Petroleum Engineer. Discuss the logging Programme with the Logging Engineer to ensure he understands the log combinations required and the order that the tools will be run. The Programme should also be explained to the Drilling Supervisor and Drilling Engineer. Ensure that a second logging cable is on board as backup in order to prevent delays should fishing operations take place. Ensure that all the tools required for the job are on board and have been checked by the engineer well in advance of logging operations. Back up tools should also be checked (if available). Ensure that the Logging Engineer is provided with the following data: Field name, well number, location (geographical and UTM co-ordinates) water depth, RKB elevation. Logging Programme, level and run numbers. Drillers TD, hole size, size and depth of the last casing. Mud type and parameters, density, viscosity, chlorides, fluid loss, cake etc. Circulation time prior to POOH to log. Time when circulation stopped. Hole conditions (deviation, doglegs, tight spots etc.). Deviation survey records if TVD logs are required. Information on expected BHT and pressure. Details of rush prints, field prints and processed data required. Copies of logs from surrounding wells and the last logs run in the hole. Expected formation tops and hydrocarbon bearing intervals. Ensure that best practice is followed regarding pulling out of the hole prior to logging. If drilling with water based mud, a mud sample should be taken prior to stop of circulation.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 32 of 75
The mud Engineer should measure Rm, Rmf, Rmc and record the measured temperature of the sample. This temperature must not be derived from charts later. Ensure that the pre-job safety meeting has taken place with the drilling supervisor and tool pusher prior to logging to discuss the procedure and contingency plans for the logging operation. Advise the Logging Engineer of the depth control procedures to be used. Unless otherwise informed by the Operations Geologist on wireline conveyed operations the GR curve from the first logging run (up log) is to be used as the depth standard and that other logs must be tied in to it. 9.1.4
Pre-job planning meeting
To ensure a safely executed and smooth logging job pre-job planning is extremely important. There should have already been a pre-logging planning meeting held in town prior to every wireline logging operation. There should be a detailed logging programme generated from this meeting to compliment the logging programme within the drilling programme. The offshore pre-job meeting should be held at least 1 day prior to logging and be attended by a minimum of the logging engineers and the Well Site geologist/and or petroleum engineer, although presence of the drilling supervisor & tool pusher is recommended. In the case of drill pipe conveyed logging (TLC), pipe recovery, or through drill pipe operations the supervisor, tool pusher and driller must attend the meeting. In the planning meeting the following points should be addressed: § Discussion of current relevant geological and drilling issues § Discussion of safety issues § Radioactivity § Explosives (if in use). § Well control issues § Tool sticking § Rig up § Mud § Equipment lifts § Handling of equipments/tools § Status of logging company personnel on board § Status of logging equipment on board § Missing equipment § Preparation § Back-up § Problems § Finalisation of logging programme § Programme changes § Tool sketches and auxiliary equipment § Logging intervals / pressures points / stations / sidewall cores etc § Special procedures & equipment for difficult conditions § Review of past experiences from other wells § Data / product delivery & data transmission § Review of onshore planning meeting minutes § Review of contingency planning § Tool / pipe sticking § Tool not reaching TD § Lost circulation problems § Tool failures 9.1.5
Supervision of logging operation
When supervising the logging operation, the Well Site Geologist (and/or petroleum engineer when onsite) must ensure that the logging programme is carried out with a minimum of both down time (not directly attributable to the logging service company) & lost time (directly attributable to the logging service company).
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 33 of 75
By following the quality control procedures, the Well Site Geologist will ensure that the final product is as accurate as possible and meets Statoil’s standards. In certain cases Petrophysicist, reservoir engineers or geophysicists may be onsite to supervise key operations. If so they will be responsible for quality control of the applicable logs. 9.1.6
Real time Quality control
Application of an easy to remember method of real time quality control is important. Use the "ROCKS" method. The letters of ROCKS spell out the key principles of log quality control as follows: R - REPEATABILITY All logs should be checked for the quality of repeatability by running a repeat section and ensuring that it matches within a specified tolerance with the main pass. This should be displayed on the display as an overlay of the curves from the 2 passes. (Repeat analysis) O - OFFSET LOGS Logs made on nearby wells should always be available and compared with the logs being run. C - CALIBRATIONS All standard calibrations and checks should be made prior to logging, should be within tolerance and displayed on the log. K - KNOWN RESPONSE All logging tools give specific readings in specific conditions (for example a sonic tool should read 57 ms/ft in casing); these should be checked and displayed. In addition tool response should show specific expected trends in certain conditions (for example shallow resistivity should read lower than deep resistivity in a permeable oil zone drilled with water based mud). S - STANDARD OPERATING PROCEDURES The logging company’s standard operating procedures should always be followed. For example, correct logging speeds, correct stand-off or centralization, setting of parameters for environmental corrections etc. 9.1.7
Checks while logging
THE WELL SITE GEOLOGIST SHOULD BE IN THE LOGGING UNIT WHILE LOGGING. If a Petrophysicist or petroleum engineers is offshore he/she will witness the logging operation. Ensure that calibration procedures are carried out and that they are within the limits recommended by the logging company. Check the depth of the casing shoe and TD. Hole fill may reduce loggers TD compared to drillers TD. The stretch correction applied to the logging cable can sometimes cause loggers TD to be deeper than drillers TD. Ensure the various curves are on depth with each other. Depth tie in is by means of the GR. Ensure that sufficient overlap exists with previous runs to provide a clear tie in either through casing or in open hole. The repeat section (which should be at least 50m) is normally run from TD and up. Insist that the repeat is run over a section of hole showing contrasting log character and that the section is long enough to prove repeatability. When logging the reservoir, repeat sections should be run in the reservoir interval. If the hole is sticky, it may be better to make the main log first and then take the repeat section at the top of the logged interval. The neutron log can read through casing and can therefore be useful to tie in to previous runs. Continuously check the log on the monitor with a log from a near by well and/or the lithology for typical responses, formation tops and hydrocarbon intervals. Unusual log responses should be questioned. Check that porosity logs give the expected response in Salt or Anhydrite. Check that the resistivity and conductivity curves correspond. Watch for cycle skipping and noise on the sonic. If severe, run the tool at a slower speed or in extreme cases consider running it ex-centralized. Check for cyclic variations or sine wave patterns, especially on the S.P. curve. The occurrence of the latter may indicate a magnetized cable drum. Additional information on the logging operation or abnormal repairs should be explained in the remarks section. 9.1.8
Checks after Logging
Ensure that the log has good contrast, is clean and has no evidence of electrical interference. Check that before and after calibrations are attached to the 1:200 scale log and show no significant variation, that scales and curve coding are to Statoil requirements and attached to the top and bottom of the log. Check that the log is actually recorded
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 34 of 75
at the scale stated on the heading. Scales may be changed from standard if the bulk of the log runs along the edge of the log track, on and off backup. Check that: § Scale changes, intervals of anomalous response, baseline shifts, tool sticking points, total depth, casing points and back up curves are clearly labelled. § Curve coding is to Statoil standard. § The repeatability of logs. § The log is on depth with previous runs and that all curves are on depth with each other. At least 30 m of overlap has been recorded or that the GR, Neutron, Sonic and calliper have been recorded 30 m into the casing. § All details on the log heading have been filled out correctly, according to Link: Standard Operational Procedure (SOP). § The three BHT have been recorded with the circulation time before POOH and the elapsed time since circulation. § The Rm, Rmf, Rmc and temperature have been recorded.
§
9.1.9
Log Headings
Standard Scales and Codes In order to facilitate the use of logs it is required to have standardised coding (dots, dashes, lines etc.) for the various log display formats. These may be changed from time to time or may vary from area to area. The Well Site Geologist will ensure that these standards are followed by the different service companies employed on the rigs. It is equally important to use standard scales, 1:500 and 1:200, unless otherwise decided.
9.1.10 Log Numbering The log run number should always be displayed on the heading next to the log name. A system of numbering logs is applied in all operating areas. A number (starting with 1) represents a series of tools (suite) run at a particular level and this number is incremented every time the logging company rigs up at a NEW depth. A letter after the number (1A) represents the number of times a particular tool has been run successfully, starting with A and advancing each time the log is run. If a "Super combo" run is made which results in several different log prints being produced, especial care most be taken as in any well, successive logs of the same type must follow the sequence A, B, C, D.... without omission or repetition. Thus, while the level number for all the component logs of a super combo will necessarily be the same, the letter denoting number of times run will probably be different for the various logs. In this case, all the component letters should be reported whenever the super combo is concerned (e.g. AIT/DSI/LDL/CNL/NGL/SP 3C/B/A), whereas only the relevant letters are reported for the individual logs (e.g. AIT/DSI/GR/SP 3C, LDL/CNL/GR/CAL 3B, NGL 3A). Only log runs resulting in a log being produced and accepted should have a new letter. Misrun should be reported as such with the same letter until a good log is made.
9.1.11 Logging Service Bills & Invoices In order to ensure that wireline logging bills presented by the logging company at the well site are correctly filled in, these bills should be checked and signed by both the responsible Well Site Geologist and the Drilling Supervisor/Assistant Supervisor. Bearing in mind that these bills are often made at the end of a long logging job where errors can easily be made, it is very important that all items on the bill are checked thoroughly to ease later controlling of the bill when it gets into the Statoil system. The signing of the bill is to control that the work has in fact been carried out.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 35 of 75
9.1.12 Reporting Procedures (Logging Report) A logging report form should be filled out for each log run in the hole, successful or not, Link to Logging report form. Ensure that maximum recorded temperatures are reported. If these are not from TD, comment in the section for comments on Operations. Explain any lost time, tool failures, hole problems etc., in the same section. Any anomalous log response, intervals of poor log quality, cycle skipping etc. should be noted and explained in the section for comments on log quality. One copy of the Logging report should go into the Well site Geologists well file and a copy be sent to the Operations Geologist.
9.2 9.2.1
Borehole Seismic (VSP) Introduction
The Vertical Seismic Profile (VSP), also commonly known as borehole or well seismic, is a mature seismic method used to study near-well properties. The method differs from surface seismic because the sensors are placed down hole and the source can be either at the surface or down hole as well. Traditionally VSP surveys have been acquired to provide a vertical time-depth curve that helps tie 2D or 3D surface seismic data to seismic markers in the well. However, vertical time-depth curves are just one small example of the information a VSP survey can provide. Because VSP surveys use 3-component sensor array tools that are positioned at known depths in the well, VSP data are the best link between surface seismic and log data. This in turn connects reservoir properties to a real seismic response. Integrating VSP deliverables such as time-depth curves, calibrated velocity models, Pp, Ps, and shear wave images, and anisotropy parameters can significantly increase the value and confidence in existing and new reservoir models. 9.2.2
Responsibilities
The Well Site Geologist, Logging Engineer and/or a representative from Statoil’s VSP group will be responsible for the quality control of the Vertical Seismic Profiling (VSP) operations. Detailed information on operation procedures can be found in the best practice document: "VSP processing and sonic log calibration“. Relevant checklist for the VSP operation (“Offshore Guidelines”) can also be found on EaRTh Web (http://intranet.statoil.no/earthweb). The Well Site geologist shall: Ensure that the logging is performed according to the programme/given procedure delivered by the VSP group. Go through the logging programme with Logging contractor. Ensure that Logging contractor are provided with all necessary input data (final well position, final survey listing, GR log, final casing programme, if available, other useful logs, such as CBL etc. Be present when doing the first GR correlation (to decide what shift to use for tie in VSP depth with reference depth (from first logging run i.e.). Ensure that “Contractor’s field report” is distributed to Statoil VSP group asap.
The Statoil VSP group can be contacted if there are questions or problems during the operation, phone number will be listed in the VSP programme. The Operations Geologist and/or Logging Engineer on duty must be kept updated on the status of the VSP operation.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 36 of 75
9.2.3
Planning
The Well Project onshore will normally delegate the detailed VSP planning to the VSP group in Statoil. The Operations Geologist will be responsible for giving the special instructions and/or procedures to be followed during the VSP operations. If the operations are supervised by the VSP group, they are responsible for keeping the Operations Geologist and/or Logging Engineer on duty updated. The instructions will depend on which type of VSP to be performed. Check Shot: Measurement of the seismic travel time down to specific levels. All formation tops should be included in the list of defined levels. The source is hanging from the rig in a fixed position. Rig Source VSP: The source is hanging from the rig in a fixed position. Also sometimes referred to as Zero Offset VSP. Normal Incidence VSP: The source is hanging from a boat crane and positioned such that firing positions are vertically above the recording array for all levels. Fixed Offset VSP: The source is hanging from a boat crane. Source is positioned at a fixed location away from the rig. Walk-Away VSP: The source is towed by a boat, which moves along a given profile or profiles.
9.2.4
Before the survey (Before logging operation)
All the necessary equipment has to be checked to be working satisfactory. Noise from the rig and nearby boats should be minimized. The Drilling Supervisor and the Platform Manager should be informed in order to stop noisy work, both electrical and mechanical noise (welding, pumping etc.) during logging. The depth of the guns (Reference level = MSL) and the hydrophone has to be registered, and in addition, the distance and the direction from the well to the guns must be noted. All relevant information for the VSP operation shall be logged in the contractor’s field report. The Rotary Table (RKB) should be used as reference level for the depth measurement. The "zero point" shall be checked with the geophone hanging in the rotary table. This check has to be repeated after the logging operations, and differences larger than 2m should be reported to the Operations Geologist/VSP group immediately. If the VSP operations are performed in an open hole, remember to check the levels against the caliper log, especially in the rat-hole beneath the last casing shoe. Check if there are other disturbing seismic surveys in the nearby surroundings. Coordinating might then be necessary. 9.2.5
During the survey (The logging operation)
A checklist for the VSP operations can be found on the EaRTh Web. In addition a detailed checklist will also be included in the VSP logging programme (last page). When entering the hole, at least 2 RIH check-shots should be acquired to check the tool and at reflectors at known depths and seismic times. Details are given in the VSP logging programme/recommendations. The main logging operations will start at the deepest level (TD) and go on upwards. The check-shots performed on the way down shall be repeated when logging upwards, and should be in accordance to within +/- 2 ms. At each level the following should be checked:
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 37 of 75
At least 5 good readings shall be registered, and more if needed. A good reading will show up as a clear indisputable signal ("arrival") at the geophone. The first trough of the arrival signal gives the arrival time of the signal.
Unless otherwise specified in the VSP programme, the logging operation will normally end when the signal/noise ratio is unacceptably low and/or if the shape of the signal changes significantly. When entering multiple and/or poor cemented casing in vertical hole, the signal quality will normally deteriorate rapidly due to lack of acoustic coupling to the formation Above the 20" casing shoe, acceptable data are rarely obtained, due to casing signal arrivals. If more than one logging run is necessary (due to technical problems, look ahead a.o.), 7-9 levels from the first run(s) have to be shot again, in order to check repeatability of the tool and to be able to tie in the different parts. The Operations Geologist or the Logging Engineer should be notified if the VSP logging is terminated without fulfilling the planned programme. 9.2.6
After the survey (logging operation) - VSP data from the rig
The Well Site Geologist must assure that raw seismic data from the VSP acquisition along with the field report is transmitted onshore according to the VSP programme and logging instructions.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 38 of 75
10
Coring
10.1
Introduction
Core samples are valuable material from the wells, and they contribute to many of the analyses/interpretations to be performed. It is however, also the most time consuming and thereby the most expensive geological sampling. 10.2
The Well Site Geologist's responsibility concerning coring operation
The coring shall be in accordance with the NPD “Regulations relating to resource management in petroleum activities”, §9. Well specific information is given in the Drilling Operation Recommendation (DOR) and Drilling Operation Procedure (DOP). The Well Site Geologist shall keep the responsible Operations Geologist informed about well-related items that may obstruct or make the coring difficult and/or situations that may lead to coring in intervals not included in the Well Programme. Before starting the coring operations, the Well Site Geologist shall ascertain that the quality requirements are met with the mud (tritium added if required) and also that the coring operations are planned in a satisfactory way. It is also important that the coring is based on the requirements presented in the decision three for coring. The Well Site Geologist is responsible for: Registration and evaluation of all hydrocarbon shows and possible reservoir rocks, and in co-operation with the Operations Geologist decide if coring is necessary Decide and recommend the coring point(s) in accordance with the programme, and in co-operation with the Operations Geologist Keep close contact with the drilling-/coring personnel and give them information about expected lithology and experiences from previous wells. Make sure that the best procedures concerning core quality and core recovery and handling are followed Keep the Operations Geologist continuously updated on the status of the coring Ensure that all the equipment necessary for handling, marking, packing and transportation of the cores, are available on the rig Check that a proper area on the rig is ready for the core handling Ensure that the core(s) are treated with care and are not exposed to unnecessary damage Take the necessary/routine samples Ensure that correct measuring, labelling, sampling, description and preservation of the core(s) is done If core gamma will be run, ensure that the coring company perform core gamma when the core is laid out and marked on deck, prior to cutting Ensure that the core boxes are correctly marked and shipped at the first possible opportunity Ensure that a SJA (Safe Job Analysis) will be done on rig floor with both rig crews prior to handling of the core (drilling supervisor’s responsibility).
10.3
Methods used by Wellsite Geologist during coring operation
10.3.1 Coring programme The Coring programme will always be described in the Well Programme for the actual well. Check the DOR/DOP in addition to the coring decision tree.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 39 of 75
The programme usually consists of the following: In exploration wells at least one conventional core shall be taken from all zones containing hydrocarbons. Furthermore, necessary cores should be taken of potential source rock types and of reservoir rock types Conventional cores should be taken from the entire reservoir section in selected appraisal and development wells Coring should continue to at least below the water contact A decision three that tells when and where to start coring All non-conformances related to the Coring Programme shall be verified / discussed with the responsible Operations Geologist. Tritium tracer: Tritium might be added to the mud in front of the coring job, to be able to measure the invasion of mud into the cores. Ensure that the required tritium concentration is obtained before the core point is reached. A service company will take care of this operation. 10.3.2 Equipment for core handling Besides the ordinary coring equipment, the following equipment is necessary for a correct handling of the core (the equipment should be supplied by the coring company, the mud logging company and by Statoil): The well site geologists need to check that all relevant equipment is available Transport: The different coring companies and core laboratories can supply different kind of transport boxes. Statoil prefer the ResLab type. Transport boxes supported by ResLab are made as cubes with holes where the one meter-length core pieces are carefully placed. Corpro supply a similar type of transport boxes Transport boxes should be delivered in separate baskets for shipment. One extra basket for core shipments should be ordered, in order to prevent shipment in ordinary containers The core boxes have only one compartment and this should be made for 1m core pieces. Wooden boxes should only be used if aluminium boxes are not available! In some cases it should be considered to ship the cores onshore in 9 m lengths. Core marking/cutting: Red and black waterproof pencils are used for marking the inner barrels, red to the right. A core cutting saw with a spare saw blade. Support pieces for the inner barrel (at least 4 pieces). Chain tongs or pipe tongs to be used for removing the coring shoe, the end-caps, the lifting nipples etc.
Packing/sealing: lids and hose clamps for the inner barrels air powered screwdriver Other equipment: textile cloths for cleaning of inner barrels, hearing protection, dust masks, protection eye glasses, chisel, screw driver, geological hammer, tape measures (10 m and 2 m), sample bags and description sheets
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 40 of 75
10.3.3 Coring point decision If the geological models are well established, with reference wells in the vicinity of the current well, the coring interval will normally be decided prior to the start of the drilling. The coring point will in this case be given in the Well Programme. In areas with sparse geological information (e.g. in an exploration area), the exact coring point will be decided during drilling. The normal procedure for deciding the optimal coring point is to drill 3 to 5 metres into the formation/reservoir, after having registered a marked "drill break". The easiest way to be able to pick the optimal coring point is to keep all the drilling parameters as constant as possible. When use of MWD tool, gamma ray and resistivity logs can be used to pick the coring point if the tool reach into the reservoir. After having drilled into the formation to be cored, the bottom sample should be circulated out of the well for analysis. Positive signs are sand which gives fluorescence (oil or condensate) and/or a significant increase of the gas readings. Remember to check gas trap prior to circulating bottoms up. The Well Site Geologist shall contact the Operations Geologist prior to the coring operations and have his/hers confirmation for additional cores unless other agreements are made. 10.3.4 Coring operations The Well Site Geologist should work in close cooperation with the Coring Engineer, and thereby helping in the elimination of possible problems during the coring. Be aware that excessive filling up of the core barrels will result in possible core damage. When pulling the core out of the hole, it is important to be aware of the gas expansion, especially during the last 400 - 500 metres. It is mainly in this interval that the gas will expand, and a low pulling rate is therefore important in order to "bleed off" the pressure in a controlled way. This is especially important in situations with loose/unconsolidated formations, and in HPHT wells with low permeability reservoirs.
10.3.5 Tripping speeds The following recommendations for tripping speeds are based on numerous wells where no damage to the core has been observed. -
TD to 1600m 1600m to 400m 400m to 55m 55 m to surface
– 2 min / Stand – 3 min / Stand – 8 min / Stand – 10 min / Stand
The connection time is not included in the tripping speed. If gas is observed on the drill floor while braking down drill collar, reduce tripping speed. The normal sampling procedure for cuttings should be carried out throughout the cored interval, as a back up for a possible lost core. It should be remembered that the NPD requirements states a maximum of 3 metres between
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 41 of 75
each sample in the reservoir zone. Mud samples should also be collected when drilling through hydrocarbon bearing intervals. All necessary equipment for moving the core out of the drill floor, placing the core on a suitable place for cutting, for core description and packing should be ready in advance. It is of special importance to prepare for loose core pieces, mud samples, core chips etc. 10.3.6 Oriented cores When doing oriented coring, it is important to assure that the available knives are suitable for the formation. The scribe shoe holds the scribe knives. They are positioned in the ID of the shoe with unequal angles between each scribe knife. This identifies one of the knives as the reference knife. It is good practice to check the knife-marks on the recovered cores, for improvement related to smaller or larger knives, if the programme calls for several oriented cores. A certain survey tool is attached to the core barrel during the coring. It is very important that the Well Site Geologist immediately quality checks the survey data after each run and also transmit the data according to given procedures. 10.3.7 Handling of cores in the inner - barrel. The core should be kept in the inner-barrel. The core handling on the rig should be done as described below. If a complete description of the core is necessary, equipment for cutting a track in the inner-barrel may be considered used instead of taking the core out of the inner-barrel. The value of the information will usually not justify the possible damages on the core while taking it out of the barrel and putting it back in again. If, however, the core is taken out of the barrel it is of great importance to ascertain that the core pieces maintain their position and orientation while putting the core back in again. For safety reasons, only personnel needed for doing the job should be present at the working area while taking out the core and while cutting the core in 1 metre lengths. Personal safety equipment, ear protection, protection glasses, and the necessary permissions (for instance "hot work" permission and a Safe Job Analysis (SJA)), are mandatory for such work. 10.3.8 Core handling on the drill floor Before and during the opening of core barrels, checking for H 2S gas and hydrocarbon should be performed regularly. This is normally performed by the contractor. The different lengths of inner-barrels should be numbered before transported to the core handling area in a certified transport basket. Never transport or lift the inner barrels without transport basket. Before removing the core lengths from the drill floor, samples from the bottom of each length should be taken for description. This is of special importance if further coring/drilling operation is dependant on the information from the core (lithology and possible hydrocarbon shows). If possible, a mud sample from the inner-barrel should be collected, since this sample will be enriched by the formation liquid bled out of the core while pulling out of the hole.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 42 of 75
All core handling should be done in a way that makes as little damage as possible on the core, and it should be ascertained that the barrels are laid out in the correct succession. The practical way of doing this will, however, change from rig to rig. Only the personnel needed for doing the work should be present at the core handling area. 10.3.9 Marking The most important issue while marking the cores, is to make sure that no doubt concerning the up and down and the depth interval of each core exist when arriving at the laboratory. The inner-barrel should be cleaned and marked with waterproof pencils in red and black. The whole length of the barrel should be marked with to parallel lines, the red one to the right and the black one to the left when looking up the core from the bottom, i.e. "red to the right when looking upwards". Remember to put core pieces that have been out of the barrel, back in the correct place again.
2004
2004
2003
2003
The top of the core should be localized and the barrel should be cut at that point. The core will then be marked with the correct depth from the top and downward. The marking should be a short line and the depth values for each meter and at the end of the core barrel.
A list ("tally") should be made, in which the top and the bottom of each of the planned core lengths/core pieces are registered. Lost core material is supposed to be lost from the bottom, and the total length of the core is registered in percent of the cored interval. The utility-percent is calculated based on the total barrel length. The possibility of over pressured gas trapped in the inner-barrel, should never be forgotten, and it is important not to stand in front of the core ends while working on the core. This is especially important when using gel and in HPHT wells! 10.3.10Core Gamma A core gamma might be run after marking of the core has been done. The coring personnel will perform this job. It is important that the core gamma batteries are checked by the contractor in front of the operation. 10.3.11Core cutting Existence of a clearing between the core and the inner-barrel should be checked before any cutting action of the core starts. If no such clearing exists and in addition, trapped gas is suspected, holes should be drilled in the innerbarrel for ventilation unless ventilated tubes are used. Trapped gas in the inner-barrel may cause a dangerous situation while cutting the cores, as the core material may be expelled from the inner-barrel at a high speed. While sawing/cutting the core, a fat-pencil should primarily be used for greasing and cooling of the saw blade. The core/core barrel should never be exposed to water. The core shall always be cut at exact every meter mark. NB- use eye, ear and breathing protection when sawing the core into meter lengths.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 43 of 75
10.3.12Sampling and core description During the handling of the core, from drill floor until it is placed in the core box, it is important to look for and to register damage on the core, such as washouts, sticking and/or crushing. Link: Best practice core descriptions.
in case of jamming of the core, it is important to record the actual depth interval. any correction of the core length will be based on observations from the previous core/core results. samples should be collected from all the cuts and from the top and the bottom of the core. the Mud Logging Engineers shall collect cuttings as usual during coring if cuttings are available. 10.3.13Packing of cores
If the core does not fill up all of the space in the inner-barrel, the "empty space" shall be stuffed for instance with textile rugs in a plastic bag or with other suitable materials. The textile must not have direct contact with the core. The inner-barrel should be sealed in both ends by plastic lids and tube clamps. The lids shall be marked with core number and depth. Loose core pieces should be packed in plastic bags or in a suitable length of inner-barrel. It is important that no doubt about up/down and depth exist. The core is packed/transported in special core boxes. The core must be stabilized in the boxes. Information such as the well number, the core number, top / bottom and from/to depths for the core pieces shall be stored inside the core transport boxes. The only information outside the transport boxes is the well-, core- and box numbers and the total number of boxes, (e.g. box no. 2 of 19). 10.3.14Shipment of cores The transport core boxes shall be placed in the special containers in which the boxes were delivered and then be shipped to the core handling company onshore at the first possible opportunity. Avoid loading and transport in very bad weather. It is required that the transport containers have shock log sensors activated during transport from the rig to the laboratory. In winter time it is required to use containers with heating to avoid freezing of the core (Arctic climatic areas). In most situations the core boxes will be delivered in full baskets, which have the effect that not enough baskets will be available if the coring goes on for a long time and cores are shipped onshore in half filled baskets. It is therefore important to have some extra baskets on the rig. If the core boxes for some reason have to be shipped by helicopter, the crane operator and other involved personnel should be contacted in advance. A 1 metre 4" core in a box has a weight of approx. 30 kilos and 1 metre 5 1/2" core will have a weight of 50 kilos. Since the cores may be fragile, such boxes should be handled in a controlled way. "Handle with care" tags should be considered, especially when unconsolidated core material are shipped ashore. A dispatch note with well- and core number, and also the total number of boxes, has to be prepared. A detailed packing list with the content of each box and with to/from depths, shall be enclosed with the dispatch note. The dispatch note may be placed in one of the core boxes which then will be marked "Dispatch note inside", or it may be forwarded by putting it in an envelope with the receivers address and sending it together with the other papers from the rig. On the "cargo manifest" no details are required, only the number of boxes and a notification that they contains "core samples" or "geological material".
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 44 of 75
10.4
Gel filled inner-barrels
This coring method, in which the core will displace a gel material in the inner-barrel, will minimize the contact between the mud and the core. It may possibly also have a "greasing" effect that thereby may reduce the possibility of getting stuck while coring (jamming). The gel is supposed to be in a liquid state while influenced by the pressure and temperature conditions in the well, but in a viscous state at the rig. In principle the handling of cores in gel-filled inner-barrels are as for other cores, but due to the gel, situations in which the pressure is not properly "bled off" have been experienced. This may cause problems while measuring, marking and dividing the cores, since the cores may expand/float inside the inner-barrels and thereby create empty intervals between the core pieces. In such situations it is impossible to measure and mark the core before it is cut. The normal practice has been to mark the top of the core with correct depth and thereafter measuring/marking the inner-barrel/"core" according to normal procedure, but without the depth marks and instead using the "core number" together with the top/bottom of piece 1, 2, 3, and so on. The final measurements have been done onshore. An alternative way of doing this is to ship the core onshore in 9 metres lengths. The advantage with this procedure is that the core is less exposed for damages, the disadvantage however, is that less of the core is exposed for inspection. As described above, gel filled core barrels may cause some extra work compared to ordinary cores. The use of gel in HPHT wells with low permeability reservoirs will increase the above-mentioned problems. 10.5
Handling of unconsolidated core material
Several techniques exist: injection of gypsum, resin, exposure in dry ice and injection of foam. In some of these techniques the core material is moulded in an either gypsum or epoxy material inside the core barrel. The coring/laboratory company will perform the preservation work on the rig. 10.6
Special analyses, sealed core ("seal peal")
Specific procedures/sampling programme connected to special studies, such as saturation measurements, wetting preferences etc., will be included in the coring programme. The service companies will have personnel on the rig to perform such special studies, to use tracer in the mud and to drill out, pack and ship core plugs for such purposes. When using inner-barrels, special sealing procedures will usually not be necessary. Experience shows that the normal sealing of the inner-barrel is sufficient. If necessary, samples for a special sealing on the rig (seal peals), may be required. Special guidelines will then be given. (15 cm seal peal/1 m sand section) If rock mechanical studies are required parts of the core that contains shale will be stored in base oil.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 45 of 75
11
Sidewall coring
11.1
Introduction
The Well Site Geologist shall ascertain that sampling of sidewall cores is performed according to the programme and the mandatory and guiding documents for logging.
11.2
Objectives
The objectives of acquiring sidewall cores may be several, the following included: Geochemistry (source rock evaluation) Biostratigraphy Lithology (correlating to wireline logs or for reservoir purposes) Por. / perm measurements Other (requirements from the licence partners, the NPD etc.) The objectives will be listed in the Well Program, and depending of these, the levels for sidewall cores have to be carefully considered 11.2.1 Wellsite Geology procecures for depth control during sidewall coring The depth control will often be a critical parameter for the results of the coring, for instance in thin coal layers. The following procedures should be used: The GR should be used for the depth correlation The depth correlation should be as accurate as possible, preferably within 20cm. The GR log should be the same as the one used for picking the MSCT depths If "working" the string, thereby causing tension in the cable, is necessary in order to get the tool free, the depth correlation should be checked on a regular basis Sidewall core recovery/collection The Well Site Geologist shall supervise the sampling of the sidewall cores when they are coming out of the hole, in order to make sure that they are placed in the correct succession The samples shall be delivered from the logging company in a glass container (marked with the core number on the container lid and with well number, core number and depth on the glass itself) and placed in special boxes 11.2.2 Depths for sidewall cores
The SWC depths will refer to the wireline log depths. Based on the instructions from the Operations Geologist, a list containing depths, hole size, expected lithology and hardness (dt) will be prepared. The calliper log shall always be checked, due to the limited range of the equipment. Four-armed calliper (from dip meter i.e.) shall be used when available. If it is necessary to take sidewall cores in the reservoir, equipment for drilling out the cores in unconsolidated formations must be evaluated 11.3
Operational routines
Normally a MSCT tool is used for sidewall coring. But if CST tool is used; according to the logging company's routines radio silence will be required due to use of explosives.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 46 of 75
.
The deepest samples shall be acquired first
11.4
Use of sidewall cores
11.4.1 Geochemistry
Gamma Ray, Resistivity, Density and Calliper logs should be used in scale 1:200. The samples should be acquired either in shale or in coal formations Shale samples should be taken from intervals in which the GR has high values and the resistivity has relatively high readings (dark organic-rich shale). Coal samples should be taken from intervals with low GR readings, high resistivity and low density (less than 1.80 g/cc) readings. Samples has to be acquired from more than one coal layer in the same interval 11.4.2 Biostratigraphy
Gamma Ray (Spectralog), Resistivity and Calliper logs should be used in scale 1:200. The samples should be acquired from shale formations (if possible above and below formation/ Biostratigraphical boundaries), in intervals with the highest GR and the lowest resistivity readings. Usually this will be from the lower parts of the shale. If spectralog is available the Th/U/K relation may be used for deciding the clay type and thereby give an indication of the depositional environment, for instance whether marine shale or other shale’s are present. 11.4.3 Lithology
Sandstones are most relevant Gamma Ray and Calliper logs should be used in scale 1:200 Clean sandstones ( low GR) with a reasonable good porosity should be used, and intervals with thick mud cakes should be avoided. At least two samples from each sand unit should be acquired if possible.
11.5
Sidewall Core Equipment
The details of the equipment to be used, shall be discussed with the Logging Engineer (based on lithology/ formation hardness/sonic log, area experience etc.) For Conventional sidewall cores the MSCT (Mechanical Sidewall Coring Tool) will be used. For drilled sidewall cores it is important that the correct type of bits, length and diameter are used A complete equipment list can be furnished by the logging engineer 11.5.1 Reporting
The recovery of the sidewall coring should be reported under the logging section in the daily drilling report, in the Sidewall Coring Report form (Link Sidewall Coring Report form) and may also be reported in the remarks field of the geology section. The report should contain all sidewall cores planned, number of lost cores, number of empty cartridges, the number of accepted cores and core length The information should be reported in the Section Report The Well Site Geologist will decide which cores to be accepted. If the recovery is low, the Operations Geologist should be consulted for discussion and decision of having another run or not. Even in hard formations the cores should be at least 10 mm long in order to be accepted. The sidewall cores shall be registered on the Composite Log, and it is important that they are depth corrected according to the actual log. The logging company shall prepare a summary which shows the depth correlations, sample depths and the results (rec./lost/empty).
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 47 of 75
11.6
Description
See Chapter 3.3.4 “Sidewall core descriptions” for general information. The description has do be done based on a fresh fracture surface, free of mud/filtrate. A sharp knife may be used if necessary The core should be fully described and tested for hydrocarbons. Excess mud should be wiped form the core and any large structures noted. Care should be taken to avoid damaging or contaminating of the core and the microscopic examination should be performed on a small chip taken from the end of the core away from the well bore. The cores shall be measured and the length should be reported in millimetres. The uppermost (shallowest) core is to be described first, and similar descriptions can be repeated for the succeeding cores. It is mandatory to minimize the damage done to the cores. At depths where cores are missing, the reason for this should be noted (“type of lithology”, or “empty”) or tool failure. The description of the cores will be recorded on the sidewall core description sheet using standard abbreviations. The description sheet heading must be filled out. All SWC description sheets will be sent to the Operations office concerned as a standard routine. 11.7
Packing, marking and shipment
Samples will be sent from the rig by the first available helicopter addressed to the Operations Geologist or various service laboratories (biostrath. geochem. etc.) as outlined in the Sample Handling and Distribution instructions for each well. The Operations Geologist will give instructions on which samples should go to each laboratory, if needed. The cores shall be carefully packed in aluminium sheets and thereafter be placed in the above mentioned glass containers. The sample must be stable in the glasses. The glasses should be shipped in boxes constructed for the purpose and furnished by the logging company. Cores taken for por. / perm measurements shall be packed in air tight packaging as soon as possible. Suitable packaging will be supplied by the Operations Geologist/laboratory onshore. The air must be taken out of the packages before they are sealed with heat. The core descriptions can be reduced, if necessary, to avoid unnecessary air exposure. alternative packing in order to avoid moisture loss from the core or moisture from outside to enter the core: a) The core should be wrapped in plastic foil (Glad pack) to seal the sample off from air exposure. Make sure that no air pockets exist against the core. b) Put the core into a plastic bag, evacuate all air by tightening the bag around the core and seal off with tape to prevent any moisture from entering c) Place the core in a suitable plastic container supplied with screw cap d) Wrap slightly water moistened paper around the sample as shock absorbent. Make sure that no excess water is present. e) Tighten the lid to ensure that plastic container is air/water tight
The core should be addressed to the Operations Geologist, unless otherwise is agreed. A manifest should be included inside each box A copy of this manifest should be given to the Operations Geologist with the addition of the address to which the samples were sent. A copy of the Sample description sheet may also be included.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 48 of 75
12
Other services
12.1
Introduction
In order to fulfil the responsibility for geological data acquisition and data quality, it is important to be acquainted with the different services available in the market, for instance geochemistry services (GHM, OSA i.e.), FLAIR (gas analysis) and onsite Biostratigraphy. For this reason it is important that sufficient background documentation (e.g. quality control manuals) are available on the rig/platform (onsite). Concerning coring, sidewall coring, VSP and wireline logging, reference is made to the respective chapters in this document and in the task documents for wireline logging and MWD/LWD. Other procedures for acquiring, reporting and shipping data shall be agreed with the Operations Geologist in each specific case. The service companies report shall be based on observations and registrations performed with their own equipment. They are obliged to relate to Statoil's requirements for securing data when handling Statoil's data. 12.2
Wellsite Geology Requirements concerning other services
The Wellsite Geologist shall; -
-
The service companies should at any time have enough and competent personnel on the rig. The companies are also obliged to appoint a dedicated contact person ("unit manager"), and to prepare a list of the personnel planned for the specific job. If, for some reason, it is necessary to use personnel that are not on this list, Statoil shall be informed in advance, also about the reason for the change. Ensure that sufficient back ground information is available ensure that the data collected by the companies are reported according to best practise.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 49 of 75
12.3
Forms for reporting
Link to all forms with examples in appendix: Standard sample description form Caving description form Conventional Core Description Core Summary sheet Core chip description Core description sheet from Winlog Logging report form Sidewall Core Description sheet Sidewall Coring Report form Summary of lithological descriptions (XL-file) Risk log Cross-section DBR; Daily, Section report, Experience report Geological Morning Report NPD report/Shallow gas report Evaluation of service companies Detailed logging operation report The Geology Qualification scheme should be used for this purpose
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 50 of 75
App A
Lithological Description
A.1
Introduction
The lithological description must be carried out as objective as possible, and in an orderly manner. Continuity of quality and form is required between Geologists working on different shifts and on various rigs. Cuttings, rock pieces from cores and sidewall cores shall be examined by use of a microscope while they are wet, and the description shall be in accordance with the following "Procedure for rock description". The rock descriptions shall be carried out on the Statoil standard sample description sheet. Standard word abbreviations shall be used (see Appendix D). A.2
Procedure for rock description
The rock properties should be described in a given sequence and should be applied to all rock types. An uniform basic approach has certain advantages: 1) Ensures all important properties are recorded. 2) Increases uniformity of description among Well Site Geologists. 3) Reduces problems in obtaining specific information from description. For fine clastic sediments the grain size will not be described and for limestone the crystal size will be described instead of the grain size. By excluding some properties, which are not relevant for a given lithology, the mentioned standard, given below, may be used for most lithology.
Rock name Modified rock name Colour Dominant mineralogy Texture Grain - /Crystal size Physical Texture Grain - /Crystal shape Sorting Matrix Cementing Hardness Structures (sedimentary and diagenetic) Fossils Porosity and permeability Hydrocarbon indications Pollution Other relevant parameters
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 51 of 75
A.2.1 Rock names Definitions of ordinary rock types: Conglomerate/gravel: A clastic sediment comprising grains/fragments with a diameter greater than 2mm. Sand/sandstone: A clastic sediment comprising grains/fragments with diameter in the range 2 - 0.063mm. Silt/siltstone: A clastic sediment comprising grains/fragments with diameter in the range 0.063 - 0.004mm. Clay: A clastic sediment comprising grains/fragments with diameter less than 0.004mm. Claystone: Petrified clay without stratification and cleavage Shale: Petrified clay with stratification and cleavage Chert (Flint): Hard and extremely tight and compact cryptocrystalline sedimentary rock comprising mainly cryptocrystalline silica and minor amounts of micro- and cryptocrystalline quartz and amorphous silica. The fracture surfaces are smooth and concoidale. Limestone: Sedimentary carbonate rock containing more than 50% CaCO 3, which means the minerals calcite or/and aragonite. Chalk: A limestone created of calcium remnants from pelagic organisms. Dolomite: A sedimentary carbonate rock containing more than 50% of the mineral dolomite or a limestone that is rich in magnesium-carbonate. Marl: Consists of 40-60% limestone/dolomite mud and 60-40% clay. The term marl should be used for rocks with low grade of consolidation. Consolidated rocks are designated as limestone with clay content or as claystone with a lime content, depending on the composition. Lignite/coal: The carbon content comprises more than 50% of the rock. Tuff: Contains more than 50% volcanic ashes. Anhydrite: Calcium phosphate, CaSO4, exists with different crystal forms, usually relatively coarse crystalline and either clear, white or greyish. Gypsum: Calcium sulphate with crystalline water, CaSo42H2O. Consist of usually clear and coarse crystals. Salt: Halite, usually clear. A.2.2 Modified rock names If the rock, besides the main lithology, contains other prominent elements, either related to the texture or to the composition, and these elements constitute at least 20% of the rock, they shall be described as modified rock
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 52 of 75
names. If the content is less than 20%, the elements will be classified as other components (see chapter B.2.13 in this Appendix). opal chalcedony microgranular quartz
calsium carbonate limestone
siliceous limestone
limestone
50
50
50
claystone argillaceous sandstone
sandy claystone
claystone clay
sand
When describing limestone it should be classified (modified) according to Dunham (1962), Classification of Carbonate Rocks according to Depositional Texture (p.108-121) CLASSIFICATION ACCORDING TO DEPOSITIONAL TEXTURE Recognizable depositional texture Original components not bound together during deposition Contains mud (particles of clay and fine silt size) Mud supported
Lacks mud
Grain supported
Less than 10% grains
More than 10% grains
Mud present between grains
Lacs mud, clean grains
Mudstone Slamstein (Mdst)
Wackestone Vakkestein (Wkst)
Packstone Pakkestein (Pkst)
Grainstone Kornstein (Grst)
Original components bound together during deposition as shown by intergrown skeletal matter, lamination contrary to gravity, or sedimentfloored cavities that are roofed over by organic or questionably organic matter and too large to interstices.
Boundstone Festestein (Bdst)
Irrecognizable depositional texture
Classification by means of physical texture or diagenesis
Crystalline carbonate Krystallinsk karbonat Xln (Dol/Ls)
(Modified after Dunham 1962)
Reference is also made to Folk (1954) Classification of siliclastic rocks (NPD-Bulletin No. 7, Geostandard - A geological standard for use within the petroleum industry). Different mineralogical modification are also permitted, for instance "... calcareous, dolomitic, micaceous....". A.2.3 Colour The rock colour shall be described by using the ROCK-COLOUR CHART, distributed by the GEOLOGICAL SOCIETY OF AMERICA P.O. Box 9140 Boulder, CO 80401, USA.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 53 of 75
The colour should be described while the samples are wet, in uniform blue light and at the lowest magnification on the microscope. It is of importance to view the sample and the Rock-colour chart under identical lighting conditions. Individual cuttings can be placed beside the coloured blocks in the chart book and viewed under the microscope. Avoid placing the sample directly on the coloured block as this leads to smearing of mud and sample which masks or changes the original colour. Variations in rock colours may be described as: Laminated (laminert); the colours appears in regular alternating thin bands. Banded (båndet); the colours appears in nearly parallel lines Streaked (stripet); for elongated colour lenses. Variegated (broket); two or more colours in a non-systematic mixture. Spotted (flekket); More or less symmetrical medium size spots of one colour, scattered around in a matrix of another colour. Speckled (spettet); a colour scattered around as small speckles in a matrix of another colour. Varicoloured (flerfarget); tree or more colours with clear boundaries. Mottled (spraglet); two or more colours with indistinct and irregular boundaries. Ambiguous terms such as "buff" and "tan" should be avoided. A.2.4 Dominant Mineralogy
This should describe the main mineral constituent of the rock in the case of non- carbonate clastic i.e. quartz, and the main clastic component in the case of carbonate clastic i.e. calc arenite. A.2.5 Texture A.2.5.1
Grain-/Crystal size
The grain size should be decided by using a grain size model. Siliciclastic rocks
Grain/crystal size (mm)
Boulder (blokk) Cobble (stein) Pebble (småstein) Granule (grus) Very coarse sand Coarse sand Medium sand Fine sand Very fine sand Silt Clay
> - 256 64 - 256 4 - 64 2-4 1-2 0,5 - 1 0.25 – 0.5 0.125 – 0.25 0.063 – 0.125 0.004 – 0.063 < 0.004
A.2.5.2
Carbonate rocks/crystal size very coarse krystalline mega crystalline very coarse crystalline coarse crystalline medium crystalline fine crystalline very fine crystalline microcrystalline cryptocrystalline
Physical Texture
Grains can be denoted as: Vitreous (glassaktig) Frosted (matte) Pitted (korrodert) Coated (belagt)
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 54 of 75
Clay and shale can be: Amorphous (strukturløs) Waxy (voksaktig) Earthy (jordaktig) A.2.5.3
Grain - /crystal shape
The shape of the grains can give valuable information about the depositional history of the rock. Two components shall be described: 1. Roundness: Describes the grade of sharpness of the grain edges. The evaluation is done by a visual comparison between the grain and a reference chart (Fig. B.1). 2. Sphericity: Describes the shape of a grain compared to a ball. The evaluation is done by a visual comparison between the grain and a reference chart (Fig. B.1). A.2.6
Sorting
The sorting of the grains gives a measure of the grain size variation in the sediment. The evaluation is done by a visual comparison by using a reference chart (Fig. B.1). The type of sorting, e.g. bimodal should also be mentioned. A.2.7 Matrix The matrix of sediment is the mechanical deposited fine material between the rock grains, and it will influence porosity and permeability. Silt and clay are the most usual matrix materials. Since it is impossible to differentiate between the different clay types in the matrix (kaolin, illite etc.) by use of the equipment available on the rig, the matrix is only supposed to be described by its colour, for instance "wh cly mtx". The amount of matrix is estimated as abundant to rare. A.2.8 Cementing Cement is a term applied to authigenic grain coating and pore filling material. It is an important characteristic of any potential reservoir as it affects both porosity and permeability. The most common cement minerals are silica, calcite, dolomite and siderite. Both the amount and the type of cement shall be described.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 55 of 75
Very well sorted
Well sorted
Moderately sorted
Poorly sorted
Very poorly sorted
Classification of degrees of sorting as seen through a square hand lens. Silt- and clay- sized sediments are indicated by fine stipple. Figure B.1.
Classification: Internal
Roundness, sphericality, sorting
Status: Final
Expiry date: 2011-02-04
Page 56 of 75
A.2.9 Hardness The samples should be tested for hardness by a steel needle. The hardness is referenced to the aggregations of minerals more than to the specific grains and crystals. The following qualitative terms may be used: Loose, the grains are separated Friable (smuldrende), the grains stick together but crumble easily between the fingers Soft, the rock is easily broken/deformed Firm, the rock may be broken by the fingers Moderate hard, specific grains may be loosened by a steel needle, it is possible to break the rock Hard, impossible to loosen specific grains, cracks between the grains, it is difficult to break the rock Very hard, the rock will crack across the grains. An example is quartzite Other expressions used in connection with compaction/hardening of sediments are: Unconsolidated Plastic, used about clay, easy deformable Sticky (klebrig), sticks to a steel needle and to fingers Brittle (sprø), used about coal, easily splintered A.2.10 Cleavage The term cleavage is used in the description of fine-grained sediments (silt/clay). Rock cleavage or fissility in fine clastic is also a process of mechanical compaction and Rearrangement of grains and the degree of fissility should be described. The following explanations are used: Massive, no cleavage Blocky, cleavage across the layering Sub fissile (delvis spaltbar), cleavage sub parallel to the layering Fissile (spaltbar), cleavage parallel to the layering Splintery (splintrig), parallel and sub parallel cleavage A.2.11 Structures Sedimentary and diagenetic structures will be described below. Only minor structures are detectable in the cuttings material, and usually it is necessary to have cores or sidewall cores available in order to describe structures in a rock. Both solely descriptive expressions, such as “graded layering", and interpretative expressions, such as "stream flutes", may be used. An example of a diagenetic structure may be stylolites. Reference is made to the NPD Bulletin no.7, Geostandard - A geological standard for use within the petroleum industry, for details of different structures. A.2.12 Other components Components that constitute only a minor part of the rock volume (< 20%), may however be of importance for the interpretation of the depositional environment, and also in correlation work. The most usual components will typically be different minerals such as mica, glauconitic, pyrite etc., and fossils, lithic fragments and plant remnants. The calcium content of fine clastic rocks is supposed to be described in this context.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 57 of 75
A.2.13 Other characteristics Some rocks, especially clay, will react to contact with water and may therefore be described as: Soluble, disperses easily in water Swelling, special types of breakage shall also be described, e.g. concoidale breaks in coal. A.2.14 Porosity and permeability The porosity is defined as the empty space in a rock. Both the amount and the type of porosity shall be described, and dried cuttings shall be used for the porosity evaluation. Since this will be a visual evaluation, the amount of porosity has to be given by use of qualitative expressions, according to the following: No visual porosity porosity not seen Poor visual porosity 5 - 10% Fair visual porosity 10 - 15% Good visual porosity 15 - 20% Excellent visual porosity > 20% Different types of porosity must also be described (if possible i.e. when thin sections are available): Inter granular, porosity between individual grains or rock fragments Intra granular, porosity within the individual grains or rock fragments Inter crystalline, porosity between the individual crystals (often in dolomite) Vugg, more or less irregular cavities Cracks, due to mechanical deformation A.3
Percentage
It is difficult to quantify the percentage of the different rocks. By use of "percentage chart", (Fig. B.2, next page) it is however, possible to give a relative distribution of the different rock types. It is sufficient to give the percentage to the nearest 5%. In addition, the following expressions are used for recording fossils, minerals and other elements, as a percentage of the whole sample: Abundant 10 - 20% Trace 1 - 10% Rare > 1% Some expressions do also have a qualitative element and are used to describe repetitive lithological series: Alternating: two main rock types, each comprising between 40% and 60% of the series. Interbedded: two main rock types of which one of them constitutes between 20% and 40%. Minor: one rock type that constitutes between 10% and 20%. Trace: one rock type which constitutes >10%
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 58 of 75
1%
2%
3%
5%
7%
10%
15%
20%
25%
30%
40%
50%
Figure B.2 Percentage chart
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 59 of 75
A.4
Other relevant advice
After a duty relief the previous samples have to be checked in order to maintain continuity and regularity in the descriptions. By complying to the standard for lithological descriptions given above, the variations should not be to pronounced. Minor variations of different qualities, especially colour, may be easier to detect if several samples are placed together for comparison (multi viewing). The shape of the cuttings is influenced by several factors, including; the type of drill bit used, the use of turbine, whether the formation reacts to the mud and whether it is a highly deviated well. This must be considered during the evaluation and the description. The cuttings should be checked on the shakers before being described. Minor, but important variations in hardness, stickiness, sand content, caving and other matters may then be detected. Different portions of the sample should be examined. This may give a hint of the amount of caving, amongst other items. The cementing will also be easier described by examining bigger fragments. Be aware of caving, and make sure that they are not included in the recorded amount of material. The caving condition should be described under the remarks section. Be also aware of mud additives that may look like minerals/rock types from the drilled formation. Examples of this may be lignite (coal), LCM material, barite and gypsum.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 60 of 75
App B
Wellsite Geology responsibilities concerning Hydrocarbon Shows
The Well Site Geologist shall, without delay, inform the Drilling Supervisor about any registrations of hydrocarbons. All samples shall be analysed under UV light in order to detect possible fluorescence, and every hydrocarbon indications shall be evaluated and reported according to the prevailing routines. Accurate descriptions of hydrocarbon indications ("shows") can be of conclusive significance, and as such should be regarded as one of the most important tasks for the Well Site Geologist. Reference is made to table C.1 in order to obtain a qualitative description of the hydrocarbon shows, as uniform as possible. After the analyses, the Well Site Geologist should to be able to give an interpretation of which type of hydrocarbons are present. B.1
Registration of hydrocarbons
The registration of hydrocarbons is a continuous process. The different possible registrations are:
Ditch gas (background gas, gas peaks, trip gas, connection gas etc) Cuttings /blender gas Oil in the mud Hydrocarbon odour Oil stain and leaking of oil Fluorescent samples Dissolved hydrocarbons and fluorescence
B.2
Gas readings
B.2.1
Ditch gas
Ditch gas is created during drilling and is registered as background gas. The amount of gas is directly connected to "the amount of drilled rock pr. time unit". Increasing gas readings are therefore natural if the drilling rate is increasing. The gas readings will also increase while drilling through gas rich and/or permeable formations. The amount of gas will be influenced by the mud weight, and it is registered by burning the gas in a gas detector. Two types of gas detectors are available; a total gas detector and a gas chromatograph (In some cases the Flair gas system will be used in advance). The total gas detector will burn all of the gas and register it as C 1-equivalents. The gas chromatograph register the gases C1, C2, C3, nC4, iC4, nC5 and iC5, and the results are given in Parts Per Million (ppm). If nC4 and iC 4 are present, the Well Site Geologist has to ascertain that possible presence of nC5 and iC 5 is checked and measured on a regular basis. The Flair gas system detects gas up to C 8. Two types of degassers for separating the gas from the mud are used.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 61 of 75
1. The standard degasser is partially submerged in the mudflow, normally in the header box (shaker box). It releases the gas from the mud flowing through by means of an agitator. The gas is trapped above the mud level in a confined space that also has an outlet to air. The mud level in the header box, the amount of mud flowing through the trap and the position where it is installed in the header box affect the degasser. In addition the degassing is not very efficient, releasing mainly the light components, and will therefore give a biased picture of the gas composition in the reservoir. The newer models of this trap are installed so they are floating in the mud, thereby attempting to minimize the effect of varying mud levels. This type of gas trap is supported by all mud logging companies. 2. Geoservices have developed a "constant volume degasser", which pumps up a constant volume of mud per unit time through a flexible sampling hose. This hose can easily be positioned optimally to the mudflow. This degasser is much more independent of mudflow and mud level in the shaker box. Tests have shown that it is also much more effective releasing the heavy components from the mud, thus giving a more correct picture of the gas composition in the reservoir. FID (Flame Ionizing Detector) used for chromatography analyses is now standard equipment by all mud companies. Other available detectors are only used as an assurance in the case of FID chromatograph failure. The improved new system, "Reserval", is more accurate and has a full cycle analysis (C 1 - nC5) within 50 seconds. The system with the standard degasser gives higher readings than the "constant volume degasser". The difference in gas readings is small in concentrations lower than 1%, but increases to 5-10 times in higher gas concentrations. The standards degas machine overestimates the C1 concentration and underestimates heavier components. When comparing gas concentrations with other wells, it is important to know which method has been used. This should also be considered when using ratio plots/diagrams for evaluating the type of reservoir liquid. These plots/diagrams are usually empirical and based on data acquired by a standard degas machine. Measurements from systems with the constant volume degas machine, if available, should be preferred due to greater accuracy, and measurements from systems with standard degas machine should be used as back-up. During drilling it should be differentiated between: Background gas during drilling Maximum gas during drilling Connection gas Trip gas All of these four gas types are registered in relation to the zero line in the gas detector. The gas types shall be reported every day, as a percentage and with the related chromatograph reading.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 62 of 75
B.2.2
Cuttings gas
The registration of cuttings gas can give valuable support to the interpretation and the description of hydrocarbons. Approximately 100 grams of unwashed cuttings should be whipped in a mixer and the released gas should be registered either in a total gas detector or in a gas chromatograph. Significantly higher gas readings in the cuttings than registered as total gas, may indicate drilling through a reservoir with low permeability. B.2.3
Gas Ratio Analysis
The Gas Ratio Analysis can give valuable information/indications concerning the maturation and the reservoir potential. Ratio plots for evaluation of the reservoir liquid should primarily be based on constant volume measurements, if available. The different mud logging companies will use their own methods, but they are usually based on the same principles. Exlog's "Mud logging, Principles and Interpretations" gives a good introduction to the principles of Gas Ratio Analysis. The other companies have corresponding documentation. These analyses should be used if heavier (nC4 etc.) are present. Link: Gas Oil Ratio Analysis B.2.4
Oil in the mud
Oil may be washed out of the cuttings by the mud, and may be registered as a dark film on the mud. The mud should then be examined under UV light, and the possible colour and intensity of the fluorescence be described. It is important to ascertain that no chemicals that may react to the UV light, are used in the mud.
B.3
Shows descriptions
B.3.1
Hydrocarbon odour
The odour of hydrocarbons is usually only detectable on new fracture planes in cores, and rarely from the cuttings. The odour is described as follows: None Weak Fair Good Strong
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 63 of 75
B.3.2
Oil stain
Oil stain is detectable on cores and cuttings when the sample is examined in a microscope with normal light. The content of oil in the sample is dependant of the rate of washing while transporting the sample by the mud. This reflects the rate of permeability, and a relatively tight rock may show good oil stains. Such zones must be registered. The rate of oil stain is a function of porosity and distribution of oil in the pores. The colour of the stain will give information concerning the oil density, that is, heavy oil will have a dark colour and lighter oils will be more and more colourless. The oil colour shall be reported by: The amount The distribution (spotted, even) The colour The amount of oil colour will qualitatively be reported as: excellent, 90-100% evenly distributed good, 50-90% evenly distributed fair, 20-50% spotted/evenly distributed poor, 10-20% spotted trace, < 10% spotted B.3.3
Natural fluorescence
All samples shall be examined for fluorescence under UV light. In order to have as representative analyses on the core samples as possible, the samples should be collected from "non flushed" material. If necessary the samples have to be taken from the middle of the core. The natural fluorescence from fresh, dry or wet samples shall be registered. It is important to distinguish between hydrocarbon fluorescence and mineral fluorescence. Some ordinary minerals such as dolomite and feldspar typically will have yellow or yellow-green fluorescence, and anhydrite has blue-grey fluorescence. The minerals, possibly also the fossil fragments, will not give cut fluorescence when adding solvent. In such cases no detectable hydrocarbons shall be reported. The mineral fluorescence shall not be described, reported or drawn on the logs. In addition to mineral fluorescence, mud chemicals and greasing materials may also give fluorescence, for instance the so called "pipe dope", which gives blue-white fluorescence. As soon as fluorescence is detected, the previous samples shall be rechecked in order to ascertain that no hydrocarbons have been overlooked.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 64 of 75
The hydrocarbon fluorescence shall be described by: Distribution Intensity Colour Amount The distribution of fluorescence shall be described as: Even Mottled/patchy Spotted Pinpoint The intensity of the fluorescence should be recorded as: Dull Pale Moderate Strong/bright The colours to be used are: Approximate hydrocarbon density none 3
violet blue-white yellow-white green-white
0.785 g/cm
gas
whitish yellow
0.83-0.785 g/cm
yellow yellow-orange gold
0.88-0.83 g/cm
3
orange brown-orange
0.94-0.91 g/cm
3
brown
0.94 g/cm
condensate
3
3
light oil "Brent" oil
heavy/bitumen oil
The amount should be qualitatively reported, see chapter C.1.6. B.3.4
Cut fluorescence
Within all intervals in which hydrocarbons are suspected, the samples shall be checked for streaming fluorescence. Representative rock fragments that give fluorescence should be taken out and dried for some minutes before adding the dissolving agent. The reason for this is that the water film on a wet sample may prevent the dissolution material to have contact with possible hydrocarbons. The sample should be observed under UV light. The time of reaction, the type of dissolution, the fluorescence colour and possibly also the colour of the dried dissolution should be described. Different types of dissolution fluids are used, mostly Isopropyl Alcohol (IPA), but all of them evaporate easily and should not be inhaled. They should all be handled with care. Trichlorethane is no longer allowed, and is hence not longer used as dissolution material. (Trichlorethane might change to nerve gas if exposed to heat and UV light)
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 65 of 75
AVOID SPILL ON THE SKIN AND INHALING THE EVAPORATED LIQUID. Due to the possible health risk, samples that have been added such dissolution material should not be stored unless ventilated in a proper way. The samples should be destroyed as soon as they are described. The time of reaction should be described as: None Slow Moderate Fast Instantaneous The dissolution pattern should be described as: Flash Cloudy/blooming Streaming Ring If a sample does not show streaming fluorescence it should be broken and observed again. Colour and intensity should be described as listed in chapter C.1.7 Notice that different dissolving agents will act different and give different colours. Therefore the dissolving agent should be noted together with the description of the cut fluorescence. B.3.5
Residual dissolution(dried)
The intensity of the dissolution pattern should be described as: excellent, 90-100% evenly distributed good, 50-90% evenly distributed fair, 20-50% spotted/evenly distributed poor, 10-20% spotted trace, < 10% spotted
The dissolution pattern should be described as: Spotted Cloudy/blooming Even Ring During the evaporation process toxic gases may be released, and due to this fact the UV-box shall always be connected to a proper ventilation device.
B.3.6
Hydrocarbon shows in oil based mud
Due to the background fluorescence that sometimes exists, description of hydrocarbon shows may be more difficult in oil-based mud than in water-based mud. The base oil dissolved natural HC very good compared to water; hence there is often not much to see in cuttings. In unflushed part of cores, virgin HC shows can be observed.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 66 of 75
The background fluorescence usually has a characteristic pale yellow-green colour, and with some experience it might be possible to separate it from the base oil fluorescence. Exlog's "Logging Techniques in Oil Based Drilling Fluids", 1984, gives a detailed description of techniques related to hydrocarbon shows in oil based mud. B.4
Hydrocarbon show evaluation
The shows evaluation depends on the rock porosity, type of fluorescence and the percentage of rock-pieces with shows as given in Table C.1 below.
PERCENT OF FORMATION WITH SHOWS
POOR OR NO POROSITY, LITTLE OR NO STAIN, WEAK FLUORESCENCE, CRUSHING CUT
FAIR VIS POROSITY, FAIR VIS. STAIN, MODERATE FLUORESCENCE SLOW STREAMING CUT
GOOD POROSITY GOOD VISIBLE STAIN, BRIGHT FLUORESCENCE GOOD STREAMING CUT
FEW PIECES TO 10%
TRACE
POOR
POOR - FAIR
POOR
FAIR
FAIR - GOOD
FAIR
GOOD
GOOD - EXCELLENT
GOOD
EXCELLENT
EXCELLENT
10 - 20% 25 - 50% GREATER THAN 50%
Table C.1 Qualitative evaluation of registered hydrocarbons
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 67 of 75
App C
Abbreviations for Lithological Descriptions Note:
Classification: Internal
Abbreviations for nouns always begin with a capital letter.
Status: Final
Expiry date: 2011-02-04
Page 68 of 75
WORD
ABBREVIATION
A about
abt
above absent abundant acicular agglomerate aggregate algae, algal allochem altered alternating ammonite amorphous amount and angular anhedral anhydrite (-ic) anthracite aphanitic apparent appears approximate aragonite arenaceous argillaceous arkose (-ic) as above asphalt (ic) assemblage associated at authigenic average
ab abs abd acic Aglm Agg Alg, alg Allo alt altg Amm amor amt & ang ahd Anhy, anhy Anthr aph apr ap apprx Arag aren arg Ark, ark a.a. Asph, asph Assem assoc @ authg Av, av
B background band (-ed) barite basalt (-ic) base basement become (-ing) bed (-ed) bedding bentonite (-ic) bioclastic bioherm (-al) biomicrite bimodal biosparite WORD
bkgrd Bnd, bnd Bar Bas, bas bse Bm bcm Bd, bd Bdg Bent, bent biocl Bioh, bioh Biomi bimod Biosp ABBREVIATION
biostrom (-al) biotite bioturbated bird’s-eye bitumen (-ious)
Biost, biost Biot bioturb Bdeye Bit, bit
Classification: Internal
Status: Final
black (-ish) blade (-ed) bleeding blocky blooming blue (-ish) bored (-ing) bottom botryoid (-al) boulder boundstone brachiopod brackish branching break breccia (-ted) bright brittle brown bryozoa bubble buff burrow (-ed)
blk, blksh Bld, bld bldg blky blmg bl, blsh Bor, bor Btm Bot, bot Bld Bdst Brach brak brhg Brk, brk Brec, brec brt brit brn Bry Bubl bu Bur, bur
C calcarenite calcilutite calcirudite calcisiltite calcisphere calcite (-ic) calcareous caliche carbonaceous carbonized cavern (-ous) caving cement (-ed, -ing) cephalopod chalcedony (-ic) chalk (-y) charophyte chert (-y) chitin (-ous) chlorite (-ic) chocolate circulate (-ion) WORD
Clcar Clclt Clcrd Clslt Clcsp Calc, calctc calc cche carb cb Cav, cav Cvg Cmt, cmt Ceph Chal, chal Chk, chky Char Cht, cht Chit, chit Chlor, chlor choc circ, Circ ABBREVIATION
clastic clay (-ey) claystone clean clear cleavage cloudy cluster coal coarse coarsening upwards coated (-ing) coated grains
clas Cl, cl Clst cln clr Clvg cldy Clus c crs CU cotd, cotg, Cotg cotd gr
Expiry date: 2011-02-04
Page 69 of 75
cobble colour (-ed) common compact compare concentric conchoidal concretion (-ary) conglomerate (-ic) conodont considerable consolidated conspicuous contact contamination (-ed) content contorted coquina (-oid) coral, coralline core covered cream crenulated crinkled crinoid (-al) cross cross-bedded cross-laminated cross-stratified crumbly crumpled crush cryptocrystalline ,crystal (-line) cube, cubic cuttings
Cbl col, col com cpct cf cncn conch Conc, conc Cgl, cgl Cono cons consol conspic Ctc Contam, contam Cont cntrt Coq, coqid Cor, corln C, cov crm cren crnk Crin, crinal x x-bd x-lam x-strat crmb crpld crsh crpxln Xl, xln Cub, cub Ctgs
D dark (-er) dead debris decrease (-ing) deformed dense depauperate WORD
dk, dkr dd Deb Decr, decr def dns depau ABBREVIATION
deposited description detrital devitrified diabase diagenesis (-etic) diameter difference direct discontinous disseminated distillate ditto dolomite (-ic) dominant (-ly)
dep Descr detr devit Db Diagn, diagn Dia dif dir discon dissem Dist " or do Dol, dol dom
Classification: Internal
Status: Final
downward (-s) drilling drill stem test drusy dull
dwrd drlg DST dru dll
E earthy east echinoid elevation elongate embedded equant equivalent euhedral euxinic evaporite (-itic) excellent exposed extraclast (-ic) estimate extremely extrusive rock extrusive
ea E Ech Elev elong embd eqnt Equiv euhd eux Evap, evap ex exp Exclas, exclas est extr Exv exv
F facet (-ed) faint fair fault (-ed) fauna feet feldspar (-athic) fenestra (-al) ferruginous fibrous fine (-ly) firm fissile fissure (s) fining upwards flaggy WORD
Fac, fac fnt fr Flt, flt Fau Ft Fspr, fspr Fen, fen ferr fibr f, fnly frm fis fiss FU flg ABBREVIATION
flake, flaky flaser flat floating flora fluorescence (-ent) foliated foot foraminifer, foraminiferal formation fossil (-iferous) fracture (-d) fragment (-al) frequent fresh friable fringe (-ing)
Flk, flk flsr fl fltg Flo Fluor, fluor fol Ft Foram, foram Fm Foss, foss Frac, frac Frag, frag freq frs fri Frg, frg
Expiry date: 2011-02-04
Page 70 of 75
frosted frosted quartz grains fucoid (-al) fusulinid
fros F.Q.G. Fuc, fuc Fus
G gabbro gastropod gas generally geopetal gilsonite glass (-y) glauconite (-itic) Globigerina (-inal) gloss (-y) gneiss (-ic) good grading grain (-s, -ed) grainstone granite granite wash granule (-ar) grapestone graptolite gravel grey, grey (-ish) graywacke greasy green (-ish) grit (-ty) gypsum (-iferous)
Gab Gast G gen gept Gil Glas, glas Glauc, glauc Glob, glob Glos, glos Gns, gns gd grad Gr, gr Grst Grt G.W. Gran, gran grapst Grap Grv gry, grysh Gwke gsy gn, gnsh Gt, gt Gyp, gyp
H hackly halite (-iferous) hard heavy hematite (-ic) Heterostegina WORD
hkl Hal, hal hd hvy Hem, hem Het ABBREVIATION
heterogeneous high (-ly) homogeneous horizontal hydrocarbon hygroscopic
hetr hi hom hor Hydc hyg
I igneous rock (igneous) immediate impression inch inclusion (-ded) increasing indistinct indurated Inoceramus. in part insoluble
Ig, ig imm Imp In Incl, incl incr indst ind Inoc i.p. insl
Classification: Internal
Status: Final
instant (-eous) interbedded intercalated intercrystalline intergranular intergrown interlaminated interparticle intersticies (-itial) interval intraclast (-ic) intraparticle intrusive rock, intrusive invertebrate iridescent ironstone irregular (-ly) isopachous
inst intbd intercal intxln intgran intgn intrlam intpar Intst, intst Intvl Intclas, intclas intrapar Intr, intr Invtb irid Fe-st irr iso
J jasper joint (-ed, -ing)
Jasp Jt, jt
K kaolin (-itic)
Kao, kao
L lacustrine lamina (-tions, -ated) large laterite (-itic) lavender layer leached lens, lenticular light lignite (-itic) limestone limonite (itic) WORD
lac Lam, lam lge Lat, lat lav Lyr lchd Len, lent lt Lig, lig Ls Lim, lim ABBREVIATION
limy lithic lithographic lithology (-ic) little littoral local long loose lower lustre lutite
lmy lit lithgr Lith, lith Ltl litt loc lg lse 1 Lstr Lut
M macrofossil magnetite, magnetic manganese.mangan(fer) marble marl (-y) marlstone marine
Macrofos Mag, mag Mn, mn Mbl Mrl, mrl Mrlst marn
Expiry date: 2011-02-04
Page 71 of 75
maroon massive material matrix maximum medium member meniscus metamorphic rock, metamorphic (-osed) mica (-ceous) micrite (-ic) microcrystalline microfossil (-iferous) microfos micrograined micro-oolite micropore (-osity) micropor microspar microstylolite middle miliolid milky mineral (-ized) minor moderate mold (-ic) mollusc mosaic mottled mud (-dy) mudstone muscovite
mar mass Mat Mtrx max m or med. Mbr men Meta meta, metaph Mic, mic Micr, micr microxln Microfos, micgr Microol Micropor, Microspr Microstyl Mid Milid mky Min, min mnr mod Mol, mol Moll mos mott md, mdy Mdst Musc
N nacreous nodules (-ar) normal
nac Nod, nod nrm
WORD
ABBREVIATION
north no sample no show novaculite no visible porosity numerous
N n.s. n/s Novac n.v.p. num
O occasional ochre odour oil oil source rock olive ooid (-al) oolicast (-ic) oolite (-itic) oomold (-ic) oncolite (-oidal)
occ och od O OSR olv OO, oo Ooc, ooc Ool, 00l Oomol, oomol Onc, onc
Classification: Internal
Status: Final
opaque orange (-ish) Orbitolina organic orthoclase orthoquartzite ostracod overgrowth oxidised oyster
op or, orsh Orbit org Orth O-Qtz Ostr ovgth ox Oyst
P packstone pale paper (-y) part (-ly) particle parting parts per million patch (-y) pebble (-ly) pelecypod pellet (-al) pelletoid (-al) permeability (-able) pendular (-ous) petroleum, petroliferous phlogopite phosphate (-atic) phyllite, phyllitic phreatic pink pinkish pin-point (porosity) pisoid (~al) pisolite, pisolitic pitted plagioclase WORD
Pkst pa Pap, pap Pt, pt Par, par Ptg PPM Pch, pch Pbl, pbl Pelec Pel, pel Peld, peld Perm, k, perm Pend, pend Pet, pet Phlog Phos, phos Phyl, phyl phr pk pkish P-PPiso, piso Pisol, pisol pit Plag ABBREVIATION
planar plant plastic platy polish, polished pollen polygonal polymict (-ic) poor porcelaneous porosity, porous possible (-ly) predominant (-ly) preserved primary probable (-ly) production prominent pseudopseudo oolite (-ic) pumice-stone purple
pln Plt plas plty Pol, pol Poln poly polmc pr porcel Por, , por poss pred pres prim prob Prod prom ps Psool, psool Pst purp
Expiry date: 2011-02-04
Page 72 of 75
pyrite (-itized, -itic) pyrobitumen pyroclastic
Pyr, pyr Pybit pyrcl
Q quartz (-ose) quartzite (-ic)
Qtz, qtz Qtzt, qtzt
R radial (-ating) radiaxial range rare recemented recovery (-ered) recrystallized red (-ish) reef (-oid) remains replaced (-ment) reservoir residue (-ual) resinous rhomb (-ic) ripple rock round (-ed) rounded, frosted, pitted rubble (-bly) rudist
Rad, rad Radax rng r recem Rec, rec rexlzd rd, rdsh Rf, rf Rem rep, Repl resv Res, res rsns Rhb, rhb Rpl Rk rnd, rndd r.f.p. Rbl, rbl Rud
S saccharoidal salt (-y) salt and pepper salt water WORD
sacc Sa, sa s&p S.W. ABBREVIATION
same as above sample sand (-y) sandstone saturation (-ated) scarce scattered schist (-ose) scolecodont secondary sediment (-ary) selenite shale (-ly) Shell shelter porosity show siderite (-itic) sidewall core silica (-iceous) silky silt (-y) siltstone similar skeletal
a.a. Spl Sd, sdy Sst Sat, sat scs scat Sch, sch Scol sec Sed, sed Sel Sh, sh Shl Shlt por Shw Sid, sid S.W.C. Sil, sil slky Slt, slty Sltst sim skel
Classification: Internal
Status: Final
slabby slate (-y) slickenside (-d) slight (-ly) slow slumped small smooth soft solution, soluble somewhat sorted (-ing) south spar (-ry) sparse (-ly) speck (-led) sphalerite spherule (-itic) spicule (-ar) splintery sponge spore spotted (-y) stain (-ed, -ing) stalactitic sticky strata (-ified) streak (-ed) streaming striae (-ted) stringer stromatolite (-itic) stromatoporoid strong WORD
slb Sl, sl Slick, slick sli, slily slo slmp sml sm sft Sol, sol smwt srt, srtg s Spr, spr sps, spsly Spk, spkld Sphal Spher, spher Spic, spic Splin spg Spo sptd, spty Stn, stn stal stky Strat, strat Strk, strk strmg Stri, stri strgr Stromlt, stromlt Strom strg ABBREVIATION
structure stylolite (-itic) subangular subelongate subfissile sublithic subrounded sucrosic sulphur, sulphurous superficial oolite (-ic) surface syntaxial
Str Styl, styl sbang sbelg sbfis sblit sbrndd suc Su, su Spfool, spfool Surf syn
T tabular (-ate) tan terriginous texture (-d) thick thin thin-bedded thin section throughout tight top tough
tab tn ter Tex, tex thk thn t.b. T.S. thru ti Tp tgh
Expiry date: 2011-02-04
Page 73 of 75
trace translucent transparent trilobite tripoli (-itic) tube (-ular) tuff (-aceous) type (-ical)
Tr trnsl trnsp Tril Trip, trip Tub, tub Tf, tf Typ, typ
U unconformity unconsolidated underclay underlying uniform upper upwards
Unconf uncons Uc undly uni u uwrd
V vadose variation (able) variegated varicoloured varved vein (-ing, -ed) veinlet vermillon vertebrate vertical very very poor sample vesicular WORD
Vad, vad Var, var vgt varic vrvd Vn, vn Vnlet verm vrtb vert v V.P.S. ves ABBREVIATION
violet visible vitreous (-ified) volatile volcanic rock, volcanic vug (-gy)
vi vis vit volat Volc, volc Vug, vug
W wackestone washed residue water wavy waxy weak weathered well west white with without wood
Wkst W.R. Wtr wvy wxy wk wthd Wl, wl w wh w/ w/o Wd
Y yellow (ish)
yel, yelsh
Z zircon zone
Zr Zn
Classification: Internal
App D
Status: Final
Expiry date: 2011-02-04
Page 74 of 75
References Statoil’s requirements and local authority requirements (APOS) Directional Drilling requirements - Link Theme document Wireline logging- Link Theme document MWD/LWD- Link Theme document Geosteering- Link Theme document pore pressure- Link Theme document DST - Link Theme document Operations geology Link Theme document Geological and petroleum technical data Acquisition Usable references: Mud Logging Handbook (Whittaker) Log Data Acquisition and Quality Control (Theys)
Statoil Winlog User Guide
Geological interpretation of well logs (M.Rider). Well Site Geology Course Documentation http://npd.no Link: Standard Operational Procedures (SOP). (http://intranet.statoil.no/earthweb). Link: Best practice core descriptions Lithology Coding for Open Works Standard forms: Link to core chips description sheet. Link to Statoil’s Well Site sample descr_form Link to sidewall core description sheet. Link to The Geology Qualification scheme should be used for this purpose Gas Oil Ratio Analysis
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 75 of 75
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 1 of 75
Title:
Manual Wellsite Geology
Document no. :
Contract no.:
Classification: Internal Expiry date: 2011-02-04 Distribution date:
Project:
Distribution: Corporate Statoil Status Final Rev. no.:
Copy no.:
Author(s)/Source(s): Geo Operations
Subjects:
Remarks: Valid from:
Updated:
Responsible publisher:
Authority to approve deviations:
Techn. responsible (Organisation unit):
Techn. responsible (Name):
Date/Signature:
Responsible (Organisation unit):
Responsible (Name):
Date/Signature:
Recommended (Organisation unit):
Recommended (Name):
Date/Signature:
Approved by (Organisation unit):
Approved by (Name):
Date/Signature:
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 2 of 75
Table of contents
1
Objective............................................................................................................................................... 8
2
2 Data handling and Reporting........................................................................................................... 9
2.1
Introduction............................................................................................................................................ 9
2.2
Data from service companies................................................................................................................. 9
2.2.1
Drilling parameters................................................................................................................................. 9
2.2.2
Mud logs............................................................................................................................................... 10
2.2.3
MWD/LWD data................................................................................................................................... 10
2.2.4
Wireline................................................................................................................................................ 10
2.3
Statoil descriptions and plot/presentations........................................................................................... 10
2.3.1
Lithology Descriptions.......................................................................................................................... 10
2.3.1.1
Summary of Lithology Descriptions...................................................................................................... 11
2.3.2
Well Site Sample Descriptions............................................................................................................. 11
2.3.3
Core Description................................................................................................................................... 11
2.3.4
Sidewall Core Description.................................................................................................................... 11
2.3.5
Wellsite Geology responsibility for making the Completion Log...........................................................11
2.3.6
Pore Pressure and drilling parameters................................................................................................. 12
2.3.7
Risk Log/Trip log.................................................................................................................................. 12
2.3.8
Cross Section....................................................................................................................................... 12
2.4
Statoil Reports...................................................................................................................................... 13
2.4.1
Wellsite Geology Daily DBR reporting requirements............................................................................13
2.4.2
Partner Report...................................................................................................................................... 13
2.4.3
Pore Pressure Report........................................................................................................................... 13
2.4.4
NPD Report/Shallow Gas Report......................................................................................................... 13
2.4.5
Section Report...................................................................................................................................... 14
2.4.6
Detailed logging operation report......................................................................................................... 14
2.4.7
Experience report................................................................................................................................. 14
2.4.8
Input to Final Well Report..................................................................................................................... 14
2.4.9
Evaluation of service companies.......................................................................................................... 14
2.5
Office routines...................................................................................................................................... 15
2.5.1
Introduction/Responsibility................................................................................................................... 15
2.5.2
Daily meetings/Telephone meetings.................................................................................................... 15
2.5.3
Diary..................................................................................................................................................... 15
2.5.4
Manifest................................................................................................................................................ 16
2.5.5
Well archive.......................................................................................................................................... 16
2.5.6
Rig library............................................................................................................................................. 16
2.5.7
Inventory list......................................................................................................................................... 17
2.6
Security routines................................................................................................................................... 17
2.6.1
Geologist’s office.................................................................................................................................. 17
2.6.2
PC – Data equipment........................................................................................................................... 17
2.6.3
Sharing of information.......................................................................................................................... 18
2.6.4
Shipment.............................................................................................................................................. 18
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 3 of 75
2.6.5
Removal of data................................................................................................................................... 18
2.6.6
Samples............................................................................................................................................... 18
2.7
Training of Well Site geologists............................................................................................................ 19
3
Geological Sampling.......................................................................................................................... 20
3.1
Introduction.......................................................................................................................................... 20
3.2
Sample programme.............................................................................................................................. 20
3.2.1
Cuttings samples (drill cuttings)............................................................................................................ 20
3.3
Sample catching (drill cuttings)............................................................................................................. 22
3.4
Sample handling/packing..................................................................................................................... 22
3.4.1
Wet samples........................................................................................................................................ 22
3.4.2
Dry samples......................................................................................................................................... 23
3.4.3
Geochemical samples.......................................................................................................................... 23
3.4.4
Mud samples........................................................................................................................................ 23
3.5
Sample shipments................................................................................................................................ 23
3.6
Material Safety Data Sheet.................................................................................................................. 24
3.7
Sample preparation.............................................................................................................................. 24
3.7.1
Water based mud................................................................................................................................. 24
3.7.2
Oil based mud...................................................................................................................................... 25
4
Pore Pressure..................................................................................................................................... 26
4.1
Introduction.......................................................................................................................................... 26
4.2
Responsibilities related to pore pressure work.....................................................................................26
4.3
Pore pressure work.............................................................................................................................. 26
4.3.1
Methods and terminology..................................................................................................................... 26
4.3.2
Pore pressure calculation..................................................................................................................... 26
5
Geohazards......................................................................................................................................... 27
5.1
Shallow gas.......................................................................................................................................... 27
5.1.1
Introduction.......................................................................................................................................... 27
5.1.2
Wellsite Geology Requirements concerning Geohazards....................................................................27
5.2
Other shallow hazards.......................................................................................................................... 28
6
Directional drilling and geosteering................................................................................................. 29
6.1
Directional drilling................................................................................................................................. 29
6.2
Geosteering.......................................................................................................................................... 29
7
Mud logging........................................................................................................................................ 30
7.1.1
Introduction.......................................................................................................................................... 30
7.1.2
Equipment............................................................................................................................................ 30
7.1.3
Wellsite Geology responsibilities concerning Mud Logging quality control...........................................30
7.1.4
Products from Mudlogging Company................................................................................................... 30
8
MWD/LWD........................................................................................................................................... 32
8.1
Introduction.......................................................................................................................................... 32
8.2
Wellsite Geology Requirements concerning MWD/LWD logging.........................................................32
8.3
Methods used by Wellsite Geologist for check of MWD/LWD operation..............................................33
8.3.1
Well site check prior to logging............................................................................................................. 33
8.3.2
Check list while logging........................................................................................................................ 33
8.3.3
Checks after logging............................................................................................................................. 34
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 4 of 75
9
Wireline Logging................................................................................................................................ 35
9.1
Electrical Wireline logging.................................................................................................................... 35
9.1.1
Introduction.......................................................................................................................................... 35
9.1.2
Responsibilities.................................................................................................................................... 35
9.1.3
Checks prior to logging......................................................................................................................... 35
9.1.4
Pre-job planning meeting..................................................................................................................... 36
9.1.5
Supervision of logging operation.......................................................................................................... 37
9.1.6
Real time Quality control...................................................................................................................... 37
9.1.7
Checks while logging............................................................................................................................ 38
9.1.8
Checks after Logging........................................................................................................................... 39
9.1.9
Log Headings....................................................................................................................................... 39
9.1.10
Log Numbering..................................................................................................................................... 39
9.1.11
Logging Service Bills & Invoices........................................................................................................... 40
9.1.12
Reporting Procedures (Logging Report)............................................................................................... 40
9.2
Borehole Seismic (VSP)....................................................................................................................... 40
9.2.1
Introduction.......................................................................................................................................... 40
9.2.2
Responsibilities.................................................................................................................................... 41
9.2.3
Planning............................................................................................................................................... 41
9.2.4
Before the survey (Before logging operation).......................................................................................42
9.2.5
During the survey (The logging operation)........................................................................................... 42
9.2.6
After the survey (logging operation) - VSP data from the rig................................................................43
10
Coring.................................................................................................................................................. 44
10.1
Introduction.......................................................................................................................................... 44
10.2
The Well Site Geologist's responsibility concerning coring operation...................................................44
10.3
Methods used by Wellsite Geologist during coring operation...............................................................45
10.3.1
Coring programme............................................................................................................................... 45
10.3.2
Equipment for core handling................................................................................................................ 45
10.3.3
Coring point decision............................................................................................................................ 46
10.3.4
Coring operations................................................................................................................................. 46
10.3.5
Tripping speeds.................................................................................................................................... 46
10.3.6
Oriented cores...................................................................................................................................... 47
10.3.7
Handling of cores in the inner - barrel.................................................................................................. 47
10.3.8
Core handling on the drill floor............................................................................................................. 48
10.3.9
Marking................................................................................................................................................ 48
10.3.10 Core Gamma........................................................................................................................................ 49 10.3.11 Core cutting.......................................................................................................................................... 49 10.3.12 Sampling and core description............................................................................................................. 49 10.3.13 Packing of cores................................................................................................................................... 49 10.3.14 Shipment of cores................................................................................................................................ 50 10.4
Gel filled inner-barrels.......................................................................................................................... 50
10.5
Handling of unconsolidated core material............................................................................................ 51
10.6
Special analyses, sealed core ("seal peal").......................................................................................... 51
11
Sidewall coring................................................................................................................................... 52
11.1
Introduction.......................................................................................................................................... 52
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 5 of 75
11.2
Objectives............................................................................................................................................ 52
11.2.1
Wellsite Geology procecures for depth control during sidewall coring..................................................52
11.2.2
Depths for sidewall cores..................................................................................................................... 52
11.3
Operational routines............................................................................................................................. 53
11.4
Use of sidewall cores........................................................................................................................... 53
11.4.1
Geochemistry....................................................................................................................................... 53
11.4.2
Biostratigraphy..................................................................................................................................... 53
11.4.3
Lithology............................................................................................................................................... 53
11.5
Sidewall Core Equipment..................................................................................................................... 53
11.5.1
Reporting.............................................................................................................................................. 53
11.6
Description........................................................................................................................................... 54
11.7
Packing, marking and shipment........................................................................................................... 54
12
Other services.................................................................................................................................... 56
12.1
Introduction.......................................................................................................................................... 56
12.2
Wellsite Geology Requirements concerning other services.................................................................56
12.3
Forms for reporting............................................................................................................................... 57
App A
Lithological Description.................................................................................................................... 58
A.1
Introduction.......................................................................................................................................... 58
A.2
Procedure for rock description.............................................................................................................. 58
A.2.1
Rock names......................................................................................................................................... 59
A.2.2
Modified rock names............................................................................................................................ 60
A.2.3
Colour................................................................................................................................................... 61
A.2.4
Dominant Mineralogy........................................................................................................................... 61
A.2.5
Texture................................................................................................................................................. 61
A.2.5.1
Grain-/Crystal size................................................................................................................................ 61
A.2.5.2
Physical Texture................................................................................................................................... 62
A.2.5.3
Grain - /crystal shape........................................................................................................................... 62
A.2.6
Sorting.................................................................................................................................................. 62
A.2.7
Matrix................................................................................................................................................... 62
A.2.8
Cementing............................................................................................................................................ 63
A.2.9
Hardness.............................................................................................................................................. 65
A.2.10
Cleavage.............................................................................................................................................. 65
A.2.11
Structures............................................................................................................................................. 65
A.2.12
Other components................................................................................................................................ 66
A.2.13
Other characteristics............................................................................................................................ 66
A.2.14
Porosity and permeability..................................................................................................................... 66
A.3
Percentage........................................................................................................................................... 66
A.4
Other relevant advice........................................................................................................................... 70
App B
Wellsite Geology responsibilities concerning Hydrocarbon Shows.............................................71
B.1
Registration of hydrocarbons............................................................................................................... 71
B.2
Gas readings........................................................................................................................................ 71
B.2.1
Ditch gas.............................................................................................................................................. 71
B.2.2
Cuttings gas......................................................................................................................................... 73
B.2.3
Gas Ratio Analysis............................................................................................................................... 73
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 6 of 75
B.2.4
Oil in the mud....................................................................................................................................... 73
B.3
Shows descriptions.............................................................................................................................. 73
B.3.1
Hydrocarbon odour............................................................................................................................... 73
B.3.2
Oil stain................................................................................................................................................ 74
B.3.3
Natural fluorescence............................................................................................................................ 74
B.3.4
Cut fluorescence.................................................................................................................................. 75
B.3.5
Residual dissolution(dried)................................................................................................................... 76
B.3.6
Hydrocarbon shows in oil based mud................................................................................................... 77
B.4
Hydrocarbon show evaluation.............................................................................................................. 77
App C
Abbreviations for Lithological Descriptions....................................................................................78
App D
References.......................................................................................................................................... 91
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 7 of 75
1
Objective
This document is a guiding document concerning the tasks, responsibilities and duties for the Well Site Geologist working with exploration- and development wells. The document intends to ensure that: The Well Site Geologist acts in accordance with the prevailing authority regulations and the compulsory documents in Statoil. The requirements of the specific well project/field development are fulfilled. Reporting and communicating is conducted in a uniform, satisfactory and cost effective manner. The Role Description for Wellsite geologists is given in the Well Construction process (see I – xxxxx). The Competance description for the Well Site Geologist is given in K-23275.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 8 of 75
2
2
2.1
Introduction
Data handling and Reporting
This section gives an overview of the reporting routines and the format of standard products that are produced by the well site geologist on Statoil offshore installations. It covers the interaction between the service companies and the well site geologist, and between the well site geologist and the responsible operation geologist onshore. The reporting routines and products / formats described in this section are to be regarded as Statoil standard. General requirements for data acquisition are given in Theme document Geological and petroleum technical data Acquisition.
2.2 2.2.1
Data from service companies Drilling parameters
This is mainly applicable to exploration wells. (this is described in the mudlogging contract and as such not the responsibility of the Well Site Geologist). The drilling parameters shall be transmitted in ASCII- or LAS-format to the operations office onshore on a daily regular basis and else whenever needed. The Well Project might adjust the procedures. Average values for each 1m and 5m should be given for the parameters in the following order: DEPTH : in ‘meters’ both ‘MD’ and ‘TVD’ with reference to ‘RKB’ ROP : the rate of penetration presented in ‘meters per hour’ WOB : the weight on bit presented in ‘tons’ RPM : presented in revolutions per minute TORQ : the torque presented in ‘Newton meter’ SPP : the stand pipe pressure presented in ‘bar’ FLOW OUT : the mudflow out presented in ‘litres per minute’ TEMP OUT : the temperature out presented in ‘degrees C’ MW OUT : mud weight out presented in ‘gram per cubic centimetre’ ECD : equivalent circulation density presented in ‘gram per cubic centimetre’ Dxc : corrected drilling exponent TOT GAS : total gas presented in percent C1-5 : gas chromatograph readings for the gases C1-5 presented in ‘parts per million’
2.2.2
Mud logs
Mud logs containing drilling parameters and gas information (“Formation Evaluation Log”) should be transmitted after each hole section, or when requested. The log should be transferred to *.pdf or *.pds format before any transmission.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 9 of 75
2.2.3
MWD/LWD data
The MWD/LWD data shall be transmitted, both as a log and as a digital file to the operations office onshore on a daily, regular basis and else whenever needed. The Well Project might adjust the procedures. The normal procedures are described below.
the real time log shall be presented preferably in either *.pdf, *.pds formats which can reproduce the logs in correct scale by using available viewer-programmes . the digital format should be either in ASCII or in LAS format. The data shall be presented with 15cm increments. the MWD/LWD memory log and digital data shall be sent to the Operations Geologist when available, or loaded on to the well project team site.
2.2.4
Wireline
If no Petroleum Engineer is onsite for the logging job, the well site geologist is responsible for the electric logging operation and data quality. It is important to assure that:
Digital log data in ASCII- or LAS-format of wireline data shall be transmitted to the Operations Geologist and the Petroleum Engineer/Project Petrophysicist as soon as possible. When acquiring pressure data, these should be recorded on a spreadsheet, plotted graphically to verify the validity of the readings, and transmitted to the Petroleum engineer / Operations Geologist. Logging reports should be generated during the logging operations and forwarded to the Petroleum engineer / Operations Geologist or posted on the well project team site.
2.3 2.3.1
Statoil descriptions and plot/presentations Lithology Descriptions
Cuttings and core descriptions shall follow the standards given in Appendix A and B. The abbreviations shall follow the AAPG standard reproduced in Appendix C.
2.3.1.1
Summary of Lithology Descriptions
If the Winlog programme is used for log preparation the summary of lithological descriptions will be put into Winlog directly. If not, a special spreadsheet for the descriptions shall be prepared. The lithology description should be a summary of the sample-/core descriptions covering a defined section or a formation/group. The descriptions should be with abbreviations.
2.3.2
Well Site Sample Descriptions
The standard sample description form shall be used and written electronically. When starting a new well, a new description form/file should be used (Link to Statoil’s Wellsite sample description form). Be aware of special procedure for extending this word file, which makes it possible to have different headings on different pages. READ
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 10 of 75
the instruction at bottom of file. After each section the lithological descriptions shall be sent to the operation geologist or uploaded to the teamsite.
2.3.3
Core Description
The core log in the Winlog programme is used for the presentation of core descriptions. For core chip description the Core chip description form should be used and these descriptions are to be written electronically, Link to core chips description form. It is important to agree on depths of top and bottom of cored interval with the drilling supervisor. 2.3.4
Sidewall Core Description
The standard sidewall core description form will be used. The description shall start with the uppermost core and end with the lowermost core. Further details in Chapter 7.7. Link to sidewall core description form.
2.3.5
Wellsite Geology responsibility for making the Completion Log
The Completion Log shall be prepared in the Winlog application (Statoil’s standard application). Winlog is the log drawing software that shall be used by Statoil for preparation of completion-, core-, and trip risk logs. It can also be used to generate geological prognoses and summaries for well Programmes and final well reports. Access to the software is acquired via Access IT. The installation includes necessary font files, log patterns, and log templates. It is recommended to bookmark the following link to the Statoil Winlog user guide and get familiar with the guide before start using Winlog.
Statoil Winlog User Guide The LWD logs and/or the wireline logs, together with the sample and core descriptions, will be the primary sources for geological interpretation. The Completion Log should be updated as much as possible preferable with the last versions of wireline and/or MWD/LWD memory logs. Additional data as surveys, ROP, Gas readings, bit information and mud data shall be used. The lithology descriptions shall be with abbreviations. It is recommended that descriptions are organized with depth intervals spesifications as e.g.: 1830 – 1890m TVD: Interbedded sandstone and claystones with limestone stringers. Details about individual lithology types are then given according to depths of occurrence. Sst: clr transl Qtz ……
2.3.6
Pore Pressure and drilling parameters
The parameter plot shall be prepared by the Well Site Geologist and should be kept updated during the operations. The plot must always be easily be available for the Well Site Geologist if the mud loggers do the plotting. The Statoil standard drilling parameters plot contains: ROP, WOB, RPM, Dxc, Tot GAS, TEMP and MW OUT plotted every 5m. Shale density and calcimetry plotted on request
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 11 of 75
the main lithology and the stratigraphy shall be included connection gas, trip gas and gas peaks should be noted on the gas curve (Tot GAS) comments concerning the well head, casings, mud weight, hole problems and other relevant items should be included under "Remarks" sonic data shall be plotted when available pore pressure results/calculations, at interesting levels, should be noted with depth and together with the Dxc (actual value), Dxn (normal/trend line value) and OBG (overburden) used for the pressure calculation. Similar calculation is made by use of resistivity and sonic logs.
For further details concerning pore pressure and Predict/software see Link to Theme document pore pressure. 2.3.7
Risk Log/Trip log
Before tripping out of hole, the Well Site geologist might be asked to make a risk log for the drilling crew. The log is made by the Winlog risk log template. This log should contain information concerning hole condition and hole stability, such as information about sand intervals, coal stringers, limestone/dolomite stringers, swelling clay, inclination etc. 2.3.8
Cross Section
It might be useful to have a geological cross section with well data in order to be able to correlate the well data with the reference wells. This is mainly applicable to production wells and made onshore before operation starts. Necessary files and information will be supplied by the Operations Geologist. 2.4 2.4.1
Statoil Reports Wellsite Geology Daily DBR reporting requirements
The DBR (daily drilling report) shall be filled in every morning before 07:00 and shall cover the period from 00:00 a.m the previous day until 24:00 a.m. on the reporting day. The Well Site geologist is responsible for all information in part 7. Geology/ Pressure Data and part 14. Logging, in addition to input to the geological section report, part 1. All depths and all drilling/engineering data reported must be in agreement with similar data reported by the drilling department. In part 7. Geology/ Pressure Data the General lithology shall be written in full text and the lithology properties shall be written in abbreviations. Description of the formations shall be written into the part Preliminary zonation. In DBR, part 14.0 Logging short remarks can be added for each logging run separately. Further remarks can be added in 14.4 Logging remarks. Be aware that all information from part 14. Logging will be included in the section reports, while information from Geology remarks in part 7. Geology/ Pressure Data will not be included in the section reports. Detail about the DBR reporting system are found in the Well Site Geology Course Documentation
2.4.2
Partner Report
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 12 of 75
The daily geological morning report (applicable for exploration wells) is a part of the DBR Partner report and should be updated before 07:00 a.m. and quality controlled by the Operations Geologist prior to distribution.
2.4.3
Pore Pressure Report
The pore pressure report is a part of the daily DBR and the Section report, and shall contain the following information: Statoil's pore pressure estimation/calculation. Methods used for calculation of the pore pressure, and which data it is based upon. All pressure related problems in the well.
2.4.4
NPD Report/Shallow Gas Report
The NPD Standard sheet for reporting shallow gas are to be completed after drilling the top hole sections (including 26”), and then sent to Operations Geologists.
2.4.5
Section Report
A Section report shall be finalized for each hole section. The report is made in the DBR report system and contains information both from the geological summary in part 1 and from the daily reporting in DBR. New input shall be written into part 1. Daily Status – Section – Geological summary with relevant data regarding operations and data acquisition. In addition the description of formations has to be checked and updated in part 7. Geology/ Pressure Data – Preliminary Zonation. The logging information will also have to be checked and updated in Part 14 Logging. The purpose of the report is to register experiences and to give the first sketch of the Final Well Report.
2.4.6
Detailed logging operation report
This report shall be written in a word document for all wireline logging operation. Link: Theme Document Electrical Wireline logging.
2.4.7
Experience report
Experience report in DBR shall be written whenever relevant. This could be either positive or negative experiences, if necessary the report can be written in co-operation with drilling supervisor or drilling engineer.
2.4.8
Input to Final Well Report
In some cases the Well Site geologist might be asked to give input to the Final Well Report. The necessary files and information will then be supplied by the operation geologist.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 13 of 75
2.4.9
Evaluation of service companies
It is the responsibility of the Well Site Geologist to give input to the evaluation of the service companies on site. For mudlogging companies and the MWD/LWD service, an evaluation form is to be completed for every section. For other companies this form is to be completed for every job; example wireline, coring, core handling etc. Experiences are to be written into the form before leaving the rig, even if the section or job is not finished. The completed form should be sent to the Operations Geologists. Link to the evaluation form. Evaluation of the service representative’s performance should be included in this report and not in the DBR. The Well Site Geologist has a special responsibility to ensure quality and to report failures connected to mud logging, LWD, wireline logging and other geologically relevant items. Additional RUH or non-conformance reports shall be filled out for certain failures as: equipment failure unsuccessful logging - ("misrun") operator failure causing lost rig time For further details concerning the different services/companies and their deliveries, see the relevant sections in this document and other relevant mandatory and guiding documents.
2.5 2.5.1
Office routines Introduction/Responsibility
The Well Site Geologist has the responsibility to keep the geologist's rig office at a security standard according to the routines given below. He/she is also responsible for ordering the necessary office equipments and for keeping the well archive on the rig in a complete and updated state. Confidential geological information shall only be available to other than the geologists on a "need to know" basis.
2.5.2
Daily meetings/Telephone meetings
All rigs and platforms have regular meetings regarding the on-going operation, administrated by the Drilling Supervisor, both in the morning and in the evening for both shifts. In addition there are regular telephone meetings in the morning and at times also in the afternoon with the Well Project onshore. The timing for the different meetings may vary from rig/platform and project. The Wellsite Geologist is obliged to: Attend the morning/evening meeting on the site (rig/platform). Attend the morning/afternoon telephone meetings between the Drilling Supervisor on the rig and the Drilling Superintendent onshore. Have telephone correspondence with the Operations Geologist according to agreement Inform the Operations Geologist or duty Operations Geologist as soon as possible about all important issues, such as major deviation from geological and pore pressure prognosis, the first indications of hydrocarbons, results from coring and when the final TD is reached. Contact the Operations Geologist or duty Operations Geologist at every occasion of non-conformance related to the Well Programme and/or other mandatory documents for the Well Project.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 14 of 75
2.5.3
Diary
It is recommended to use a diary. The purpose of the diary is to ascertain that all messages, information and other communication with the operations office onshore and the service companies, are registered and thereby also available for the other geologist on the work schedule. The intention is to have the diary as a supplement to the handover between the shifts. The diary is supposed to be updated when needed, and it can adapt to the daily drilling reporting time, which following the working shifts on the rig/platform. The diary can either be electronically stored and/or as a bound book. The diary will primarily contain the following information: a brief operational status pore pressure (see mandatory and guiding documents concerning pore pressure) All correspondence between the Well Site Geologist and the Operations or Duty Geologist. Actual shipping times, correspondence with other rig personnel, orderings etc.
2.5.4
Manifest
All manifests are to be mailed to the operation geologist when samples are sent from the rig. The following information shall be included: sample type, depth intervals, mud type and mud company, time and way of dispatch, flight number or ship name, cargo number if used, container number, receivers address and contact person.
2.5.5
Well archive
On some production platforms there is a well archive with geological data. The well archive on the rig/ platform shall be updated after each well. It could include copies of all relevant reports, forms and log, as listed below: Drilling programme. Technical background documentation for the actual well (DOR, DOP, etc.) Site Survey Report Dispatch notes and possible other manifests Mud logging company's inventory list Mud logs LWD logs Wireline logs
2.5.6
Rig library
All of the mandatory and guiding documents necessary for the Well Site Geologist are available as digital document in APOS. Other documents for exploration and development wells might be available: Completion logs for reference wells OD Bulletin’s nr. 3, 4 and 5 Final Well Reports for the reference wells and other relevant data from neighbouring wells; such as section reports, electrical logs, LWD logs, mud logs and parameter plots. Statoil pore pressure course. (Rafdal 1994) Mud Logging Handbook (Whittaker) Statoil Wireline Formation Evaluation Operation Procedures, Electrical Wireline Best Practice Document
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 15 of 75
Manual for Core Handling. VSP acquisitions, processing and sonic log calibration. Schlumberger/Atlas wireline logging manuals, calibration books etc. dictionaries: English-Norwegian/Norwegian-English Technical dictionary Glossary of Geology, (Bates & Jackson)
And in addition the following documents may be useful: Log Data Acquisition and Quality Control (Theys) A new method for pore pressure evaluation by using DC-exponent and Sonic logs (J. Skagen) Internal publications/notes concerning the actual area 2.5.7
Inventory list
The geologist's office shall be furnished or have access to the following equipment: PC, monitor, printer, scanner, etc. paper shredder Communication equipment Internal and external telephone lines, fax and a PC linked to the Statoil network (Daily Drilling Report and other relevant databases).
2.6 2.6.1
Security routines Geologist’s office
The geologist's office shall at any time be kept tidy. When the Well Site Geologist leaves the office for shorter or longer periods, no restricted/confidential material shall be left at the desk, and the well file shall be copied to G: disk, and deleted from the PC. Some wells will, by the customer (the licences), be defined as "tight wells". While drilling such wells special security routines, defined by the Well Project/the Operations Geologist, will be followed. Documents that contain confidential information shall be sent onshore to be if this for some reason cannot be done on the rig. All documents shall be locked up and the PC shall also be locked if/when either Statoil's geologist or petroleum/testing engineers are not on board the rig. 2.6.2
PC – Data equipment
Only Statoil employees and personnel approved by Statoil are allowed to use Statoil's data equipment. Information of the personal ID-code and password(s) shall not be shared with other persons. The data lock shall be active as long as the office is unmanned, in order to prevent that non-Statoil personnel log on to the data equipment. It is not allowed to install copies of data programmes which is not given a data virus control
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 16 of 75
2.6.3
Sharing of information
The service companies are entitled to all the information needed in their daily work, however nothing more than that. This usually means parts of the Drilling Programme. The service companies are not allowed to share information with other service companies without permission from the Well Site Geologist. The service companies have to be informed of this practice, for instance by the Well Site Geologist or the Statoil Drilling Supervisor.
2.6.4
Shipment
Shipments of data, such as logs and reports are normally done by e-mail, memory sticks/DVD/CD, etc., and non electronic shipment of data shall only be carried out in one of the following two ways: In a locked Statoil mail bag, with helicopter/aeroplane. Hand carried by Statoil personnel, or by personnel approved by Statoil if they are going directly to the Operations office. A dispatch note shall be attached to all shipments
2.6.5
Removal of data
The Well Site Geologist has to ensure that all written documentation that have been distributed to rig personnel, are returned and filed or destroyed, at the latest when the well is finished. In situations where another operator shall use the rig, all Statoil equipment and documentation have to be removed from the geologist’s office and shipped onshore.
2.6.6
Samples
Packing, marking and shipment of samples should be carried out according to the given routines (see Chapters 4.4 and 4.5). A set of dry samples shall be kept on the rig until the well is finished. 2.7
Training of Well Site geologists
The Well Site geologist is required to actively supervise and train the trainee Well Site geologist. Link to The Geology Qualification scheme should be used for this purpose
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 17 of 75
3
Geological Sampling
3.1
Introduction
The Well Site Geologist is responsible for ensuring that sufficient material are collected according to the Well Programme, and he/she shall supervise the sampling and ensure required labelling. Authority requirements shall also be met, reference to the documents "Acts and regulations", edited by NPD (available on http://npd.no), and likewise all Statoil requirements shall be fulfilled. 3.2
Sample programme
A detailed sample programme is included in the Well Programme, and it is mandatory to comply with this. 3.2.1
Cuttings samples (drill cuttings)
The mud logging company is responsible for the catching, preparation and shipment of the samples. It is the Well Site Geologist’s responsibility to ensure that this is done according to Statoil’s requirements and as specified in the Well Programme. See Chapter 3 $9 in Link to NPD’s Ressursforskriften. 4.2.1.1 Wet samples
To be packed unwashed, usually with 10m or 3m intervals. The samples are normally collected in 5 litres buckets and processed onshore. If separate samples are collected, the samples shall contain minimum 500 g, and the NPD sample shall contain minimum 1 kg. If minor amounts of cuttings are coming over the shakers, the NPD should have 50% of it. In exploration wells sampling shall commence as soon as returns have been established, according to the programme. In development wells the sample programme might be reduced after samples have been taken from a representative selection of the wells. Normally only wet samples from the reservoir and source rocks will be collected. The intervals between the samples shall not exceed 10 m. In long hole horizontal sections with layer parallel drilling, sampling interval of 20m might be sufficient. When drilling exploration wells in potentially hydrocarbon bearing layers, the samples should be collected with intervals not exceeding 3m if conventional cores are not taken. The samples should be as representative for the interval sampled as possible and standard procedures for handling of the samples should be followed. Cuttings samples should also be collected during coring if possible, in order to have back-up material in case of lost core(s).
4.2.1.2 Dried samples
Washed and dried, normally 100 g, and minimum 10 - 20 g. One set of samples shall be prepared and stored on the rig until the well is completed. Dried samples can also be prepared in the laboratory onshore
4.2.1.3 Mud samples
Mud samples (1 litre) will normally be collected when the mud characteristics are changed and/or when introducing new chemicals/additives in the mud
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 18 of 75
In exploration wells mud samples will be collected when drilling through hydrocarbon bearing formations and into the water zone; according to data acquisition programme. Irrespective of sample intervals, mud samples shall be collected if traces of oil are registered in the mud. It may be wise to try to "skim" the oil film in order to get a sample as rich as possible for analysis. These samples shall immediately be shipped to the relevant laboratory.
4.2.1.4 Geochemical samples Samples for geochemical analysis shall be sealed, unwashed, in tin cans (or suitable plastic bottles) after adding bactericide; according to data acquisition. These samples are usually "composite samples", a part of the sample is collected together with each wet sample. 4.2.1.5 Ditch Gas samples Drill gas might be collected according to data acquisition programme. This might be done in gas bags or iso-tubes. 4.2.1.5 Sidewall Cores A detailed description of the Sidewall coring operation is found in chapter 12. 4.2.1.6 Core Sample A detailed description of the coring operation is found in chapter 11. 4.2.1.7 Fluid an Gas Sample A detailed description of the Fluid Sampling operation is found in chapter 10 and Link: Theme Document Electrical Wireline logging. 4.2.1.8 Other Sample Extra Cement and mud samples are frequently collected by the representative contractors for analysis. If not stated in the Well Programme it is normally not a Well Site Geologists responsibility. However, if alterations are made which has implications to any aspects of the Formation Evaluation it must be detected and reported. Likewise it is important that the Well Site Geologist consult the Wireline Logging Programme/Coring Programme etc. for proactive actions, like adding of Tracers to mud, verifying ditch magnets in flow line and the collection procedure for weighing the magnetic steel, if a CMR log is requested.
3.3
Sample catching (drill cuttings)
The correct "lag time" is of great importance for the sample quality and the depth control. The Well Site Geologist should ascertain that the lag time is checked on a regular basis. The following methods can be used for calculating the "lag time": Distinct marker beds identified by drilling parameters, or MWD log responses. by registration/correlation of gas peaks versus increased drilling speed ("drill break") by registration of trip gas or connection gas. In this case one has to be quite certain that the gas comes from the TD and not from a shallower level. carbide test (to be performed by the mud logging engineers). Due to a certain risk of plugging, the use of carbide should always be given a thorough consideration. Only soluble packing’s should be used.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 19 of 75
The samples are to be collected from the sample board placed underneath the shale shaker. The samples should be collected from the entire sampling interval, it is therefore important to check that the sample board is cleaned after the collection of each sample. It is the responsibility for the Well Site Geologist to establish proper routines to be followed by the sample catchers and the drilling crew, in order to prevent that the samples are washed away. The shale shaker screens should be as small scaled as possible, but big enough to enable additives to the mud and the mud through. In situations with minor amounts of return over the shale shaker or when drilling in unconsolidated sand, the samples must be collected from the "desander/desilter" ("lag time" will not be accurate). If samples are caught from other places than the shale shaker it has to be noted in the description form under “remarks”. It is a good practice to collect samples regularly from the "desander/desilter", in order to get an impression of the "normal amount" of fine sand/barite. Fast drilling in the larger hole sections causes the cuttings to build up almost instantaneously on the board after cleaning out the cuttings. Therefore the interval sampling appears as “spot samples in reality. To avoid this, only a minor portion of the returns could be guided to the board or a sampling bucket. This can in practice be done by mounting a cuttings guide tray with a choke without interference of other actions around the shakers. 3.4
Sample handling/packing
3.4.1
Wet samples
Wet samples shall either be packed in plastic bags and thereafter in cloth bags or plastic coated paper bags, or in 5 litres plastic buckets/tin cans. The bags and buckets/cans shall be marked with the company name, well number and depth/depth interval. The bags shall be placed in standard wooden boxes, on the outside marked with the company name, well number and serial letter and box number (2A, 2B, 2C,...) The depth interval shall be written on the inside of the box. The buckets shall be placed on pallets with suitable frames. Wet samples in boxes which are to be shipped by commercial aircraft (e.g. Series A paleo.) must be Enclosed in a large plastic bag and sealed to prevent leakage in the aircraft. 3.4.2
Dry samples
The dry samples shall be packed in standard paper envelopes and thereafter in cardboard boxes and transported onshore in wooden boxes. The envelopes and the cardboard boxes shall be marked with the company name, well number and depth, the transport boxes shall be marked in the same way as for wet samples.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 20 of 75
3.4.3
Geochemical samples
The samples shall be filled in tin cans; 3/4 should be filled with the sample itself and thereafter the cans should be filled up with drill water and a drop of bactericide. The cans shall be stored and shipped upside down. The sealing of the tin cans have to be checked regularly. Cans with a pressure sealing lid are recommended. In order to prevent damage to the sealing ring upon sealing, it is useful to put a board (wood) on top of the lid and then knock once on the board with the hammer. This results in an even pressure to the entire sealing ring. The cans shall be marked with the company name, well number and depth. The shipment of the cans will be in wooden boxes, marked as described above. 3.4.4
Mud samples
The mud samples should be filled in tin cans or suitable plastic bottles. One reference mud sample will be taken before the drilling operation start. The rest of the mud samples will be taken according to the sampling programme. Marking and shipment will be as for the geochemical samples. 3.5
Sample shipments
All samples shall be transported in containers. The boxes and pallets must be loaded in a stable way and secured by straps and nets. A dispatch note, with well number, sample type(s),depth intervals, mud type and mud company, box number and the amount of boxes, shall be placed in one of the boxes. This specific box has to be marked with "Dispatch note" with the receiver's address and sending it together with the other papers from the rig. The samples shall be shipped onshore to the person/institute responsible for further treatment on a regular basis (for instance weekly or after each hole section). In some situations helicopter transport may be appropriate. The dry samples shall be kept on the rig until the well is finished as a security action. It is the Operations Geologist’s responsibility to forward the samples to the laboratory/storage address. A copy of the dispatch note (Manifest) must be sent to the Operations Geologist.
3.6
Material Safety Data Sheet
To ensure that all involved personnel takes the precautions needed to handle the material in a safe manner, the following routines shall be followed for labeling and transport of geological samples: 1. The mudlogging company shall mark all samples from the rig with HSE information a. Data sheet from the mud engineer shall be available in the mudlogging unit. b. HSE-data sheet, both in Norwegian and English shall be put together with every sample shipment that is sent from the rig, both by helicopter and boat c. The manifest shall give information about sample type, depth intervals, mud type and mud company.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 21 of 75
d. If the mud type has been changed, samples from different sections must be packed in different collies. 2. Reslab will receive the samples from the rig together with HSE data sheet. a. If HSE-data sheet is missing, the sender must be informed immediately. The Statoil Operations Geologist shall also be informed and a synergi report will be written. 3. When Reslab forwards samples to geochemical- or biostrath-laboratories, a copy of all HSE data sheet’s shall be sent together with the samples. The manifest shall contain information about which mud type that has been used in the different intervals sampled. 3.7
Sample preparation
The preparation of the samples for description and storing is very important and the Well Site Geologist shall ascertain that the following standard routines are used. 3.7.1
Water based mud
the sample shall carefully be washed through a 4mm sieve and collected in a 120-micron sieve underneath. In reservoir intervals and in unconsolidated intervals, a 90-micron sieve is to be used (not in top holes) as the lowermost sieve. the water stream shall be kept on a low level, in order to avoid out washing of soft and unconsolidated formations. Due to this risk of out washing, a small amount of unwashed sample shall always be attached for description. At the same time one should be aware that not enough washing will tend to leave a thin film of dried mud around the dried sample. Re-washing in the laboratory may destroy the sample. after being washed a thin layer of cuttings shall be distributed evenly over a suitable board, in order to drain away surplus water. A tag with a notation of the correct depth shall always be attached. dry samples shall be dried slowly with low temperature, normally 40 0C.
3.7.2
Oil based mud
Only the oil component that is already in the mud, the base oil, must be used when washing the samples.
Place the sample in a coarse sieve. Put a fine sieve, 90/120 micron underneath. The sieves should thereafter be lowered in a container with base oil in such a way that all the sample material is covered by oil. Shake well and let the oil drain away. Repeat this procedure 3-5 times. remove the coarse sieve and wash the sample with rig wash or another suitable type of soap in the fine sieve another 1-2 times as described above the sample should now be placed on a sample board, and some of the same oil should be added. Distribute the sample evenly on the board and let it drain. The sample will now be ready for a microscope inspection before doing density measurements, remnants of oil film on the samples have to be removed by using a solution product (the same as being used for "shows" evaluation). The sample should thereafter be air dried before it is dropped in the column for density measurement. the dry sample procedure is the same for oil-based mud as for water-based mud.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 22 of 75
4
Pore Pressure
4.1
Introduction
The Well Site Geologist has a special responsibility connected to the pore pressure surveillance. Close cooperation with the Drilling Supervisor on the rig and the Mud Logging Engineer is needed. In wells with uncertain pore pressure prognosis and in exploration wells, a pore pressure plot shall be generated and kept updated at all times. This is particularly important in HTHP wells and when drilling wells in areas without any reliable background information. Statoil "Pore Pressure Manual" and Statoil "Pore Pressure Course Manual" (Mandatory document for pore pressure work in Statoil), "Link: Theme document pore pressure" describes the procedures to be used. All documents shall be available at well site. 4.2
Responsibilities related to pore pressure work
The main responsibilities for the Well Site Geologist are: estimation of the pore pressure in Statoil operated wells by using available software surveillance, plotting and interpretation of relevant data daily reporting to the Drilling Supervisor of the pore pressure estimate ascertain that only one pore pressure is reported to the operating office onshore, for a given depth updating the journal with the pore pressure value(s) preparation of the pore pressure summary inform the drilling management immediately if changes in the pore pressure and/or deviations from the pore pressure prognosis occur Verify results of FIT, LOT and XLOT For further details reference is made to Chapter 3.3.6 of this document and the mandatory/guiding documents mentioned above. 4.3 4.3.1
Pore pressure work Methods and terminology
The methods and the terminology to be used, and which parameters and logs to be used are described in the above mentioned mandatory/guiding documents. 4.3.2
Pore pressure calculation
Use the pore pressure software that is available on the rig/platform. Reference is made to Chapter 3.3.6 and Link: Theme document for pore pressure.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 23 of 75
5
Geohazards
5.1
Shallow gas
5.1.1
Introduction
Shallow gas is usually defined as non-commercial Hydrocarbon accumulation in younger sediments. Shallow gas typically occurs between approx. 100 meters and down to 1000 meters below seabed. In fairly unconsolidated formation and is characterized by having a high flow potential. Usually the gas occurs in local thin sandstone beds with a thickness of less than 10 meters, but occasionally the gas may occur over a large area (several kilometres in extent). Shallow gas exists all over the Norwegian continental shelf and, world wide, has caused more blowouts and rig losses than any other well control problem. Prior to finalizing the location for a well or platform, a site investigation (Site Survey) will be carried out. This, amongst other things, will be designed to detect and map shallow gas and the full report will be delivered to the NPD (the Norwegian Petroleum Directorate) together with the main drilling programme.
5.1.2
Wellsite Geology Requirements concerning Geohazards
There shall always be a Well site Geologist at the well site when drilling through possible shallow gas zones. The well site geologist shall: Have a thorough knowledge of the site survey report and the Statoil verification of site survey results Have a complete overview of prognosed shallow gas zones from the Drilling programme. Be familiar with analogous problems in neighbouring wells. Know that it is difficult to map shallow gas from seismic data and not trust blindly in the prognosis. Observe closely all possible gas “signals” from the well (ROP, LWD/MWD, ROV, gas problems when hole is tight etc.). Ensure that the rate of penetration is limited to the data acquisition rate of the LWD/MWD equipment can detect formations containing shallow gas. Report immediately to the Drilling Supervisor any indications of shallow gas. Be aware of the swabbing effect when picking up during connections.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 24 of 75
Class
Risk
0
Low risk (Class 0 shall never be given if any doubt whether shallow gas can be excluded)
I
Low/medium risk
II
High risk
III
Very high risk
5.2
Shallow gas assessment Shallow gas is NOT predicted
Indication in well No indication on MWD
Shallow gas w/ normal pressure is predicted or cannot be excluded
How to drill top hole May drill full size hole directly, Evaluate the need for pilot hole: - In a new area - If the area is known to have shallow gas - If drilling from a jack up. Drill pilot hole with sea water. If MWD indicate gas, flow check. Continue drilling.
Questionable/ shallow gas indications on MWD. Well stable with sea water Shallow gas w/ Shallow gas Consider placing casing above. If abnormal pressure is indications on necessary to get surface casing predicted MWD. Well flows deeper, use pilot hole and weighted with sea water. mud (min. 1,10 SG) when entering zone of interest. If MWD indicate gas, flow check. Continue drilling with weighted mud only. Shallow gas w/ Shallow gas abnormal pressure indications on MWD. Gas is blowing uncontrolled
Other shallow hazards
In addition to shallow gas, several other shallow hazards also exist. At the moment there are no formal requirements how these hazard should be treated, but the Well Site geologist should be aware of these. Many of these hazards are related to drilling in deep water (> 1000 m). In certain areas shallow water flow will be a potential problem. The Well Site geologist should be aware of:
Shallow water flow. Weak formation (for example ooze) Boulders/ gravel beds Shallow cemented sand Loose sands
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 25 of 75
6
Directional drilling and geo steering
6.1
Directional drilling
The different companies have different tools for directional drilling. These tools behave different and an experience with the different tools is needed to be able to plan and assist the service company during operation. 6.2
Geosteering
When geosteering a well with aid of real-time LWD logs, it is critical that the real time log quality is sufficient to make correct decisions. If any vital sensors fail during drilling, the Operations Geologist should be contacted and drilling should be stopped until the failure is corrected. Link: Theme document for Geosteering.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 26 of 75
7
Mud logging 7.1.1
Introduction
The Well site Geologist shall ensure a good data quality and that the data acquisition programme is followed. The mud logging service has two main roles during the drilling operations: As a data acquisition service, sampling, and sample handling As a safety service, to record and identify possible risks. 7.1.2
Equipment
The mudlogging equipment is stead in the mudlogging contract. 7.1.3
Wellsite Geology responsibilities concerning Mud Logging quality control
The Well Site Geologist is responsible for the quality control of both the working routines and the acquired data. The Well Site Geologist should: Be acquainted with the different instruments and their way of functioning; ascertain that they always are operational and that calibrations are performed according to the quality control manuals of the mud logging company. Ensure that the calibration of the following instruments are performed at least once a week the total gas detector the chromatograph the H2S detector The calibration of all instruments shall be documented on Statoil request. Check that all sensors are correctly located, and that maintenance and cleaning are done according to schedule. Make sure that all equipment failures are reported on RUH-forms and in DBR. Check that all received data are as correct as possible and that they are ready at the given time limits. Actual data in this respect are: drilling parameters Dxc values, the calculations have to be checked by the start of each hole section the formation evaluation log (mud log), the format has to be discussed with the Operations Geologist when starting the drilling. Check that the sample collection is performed according to the Well Programme and in accordance with Statoil's procedures. Establish a close and continuous co-operation with the mud logging personnel, especially for pore pressure calculations. Provide necessary information to the mud loggers. Ensure that working routines and procedures for the different analyses, such as calcimetry, shale density i.e. are consistent and in accordance with the service company's guidelines. 7.1.4
Products from Mudlogging Company
Each Well project will before spudding of the well, give the project's specific requirements. Statoil will usually require the following logs and other data on a regularly basis (recipients in brackets): "Formation Evaluation Log", digital/paper copy, (Operations Geologist/Well Project and rig archive) "Pressure Evaluation Log", digital/paper copy, (Operations Geologist/Well Project and rig archive) "Digital Drilling Data ", 1 m interval and 5 m interval, (Operations Geologist/Well Project and rig archive), Other logs and extra copies will be made if needed.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 27 of 75
In addition, the mud-logging engineers shall each week prepare an updated inventory list of articles of consumption (bags, boxes etc.).
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 28 of 75
8
MWD/LWD
8.1
Introduction
The purpose of this chapter is to secure a standardized planning, operation and reporting of MWD/LWD operations in Statoil. The Well Site Geologist/ Petrophysicist / Petroleum Engineer is responsible for quality control and interpretation of the LWD logs onsite. He/she is responsible for making sure that the work is performed according to, and also that the data are in accordance with the requirements given in Statoil's mandatory and guiding documents for logging ( Link to Theme document MWD/LWD). There are many reasons for running LWD:
8.2
drilling/geosteering formation evaluation/well correlation optimize the drilling operations shallow gas detection well correlation identifying formations, tops and marker beds/horizons reservoir and hydrocarbon detection casing setting deciding coring points pore pressure evaluation directional measurements measurement of down hole drilling parameters (WOB, RPM and torque), pressure and temperature in the mud column compulsory logging as replacement for wireline logging
Wellsite Geology Requirements concerning MWD/LWD logging
The Well Site Geologist / Petrophysicist/ Petroleum Engineer shall:
Be acquainted with the LWD equipment to be used and its functioning. In co-operation with the drilling management on the rig/platform, make sure that the necessary equipment, including backup equipment, is available on the rig when needed. At all time know the objective(s) for the logging operations and of the priority of the data. When preparing the BHA with the LWD tool included, make sure that the requirements related to the geological data acquisition are attended Be sure that limitations of the LWD equipment (critical RPM, pump rates, pressure drop i.e.) are considered before running the LWD tools in the hole Final logs have to be compared with the raw data and/or the "field copy", since it may happen that anomalous, but correct, readings are edited, for instance low resistivity in pyrite Ensure that all data, both plots and digital data is recorded and reported according to the requirements. Details regard standards for reporting, log presentation etc. are given in Link: Standard Operational Procedures (SOP).
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 29 of 75
8.3
Methods used by Wellsite Geologist for check of MWD/LWD operation
8.3.1
Well site check prior to logging.
Make sure to know the logging programme and its objective.
Discuss the choice of bottom hole assembly and the position of the MWD tool with the Logging Engineer and the Drilling Supervisor to make sure that it agrees with what is required to fulfil the objectives of the run.
Ensure that the tools needed and back-up equipment needed for the job is on board.
Ensure that the Logging Engineer is provided with the following correct data:
Well number, location, water depth and KB elevation. Information on expected bottom hole temperature and pressure. Maximum temperature rating is usually 150°C. Planned TD prior to each run. Make sure that the sampling rate for the tools are known such that the maximum allowed ROP for acquiring a good quality log is not exceeded (usually 3 readings per meter).
Make sure that the Kelly height sensor and signal receiver have been checked out by the engineer.
Make sure that the tool is run in the correct mode (MWD or tool face mode) for the job. 8.3.2
Check list while logging
Make sure that the logs overlap with the previous run. In the case of the need for reaming a section to fulfil this, it has to be discussed with the Operations Geologist. Check log response with previous log runs/reference logs. Make sure that the Logging Engineer routinely measures mud resistivity and temperature out and that correct correction factors for the actual hole size and tool size are being used. Accurate environmental corrections are possible only if the mud data are available. Every time the mud is changed (weight, composition etc.) a new set of mud parameters must be reported. For the GR also mud weight and barite content should be used for correction of the log. Make sure that the maximum allowable ROP is not exceeded. Continuously check log responses and question any unusual responses. Watch the shock counts on the tool if available. If excessive shocks, discuss with the Logging Engineer and recommend corrective actions to the Drilling Supervisor. In the case of a tool/sensor failure, inform the drilling supervisor and the operations geologist. POOH might be necessary.
8.3.3
Checks after logging
If failures during operation check that the tool is visually inspected after operation.
If the tool have to be rerun, consider having it changed out depending on the operating hours
In the case of sections of missing/poor data, reaming and logging of those sections on next run has to be considered.
Ensure that all data is reported according to the Statoil’s requirements
Record MWD temperature and report on daily drilling report.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 30 of 75
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 31 of 75
9
Wireline Logging
9.1
Electrical Wireline logging
9.1.1
Introduction
This chapter is a guideline for well site geologists for supervising and witness electrical wireline logging. For further details see Link: theme document Electrical Wireline Logging. This chapter does not contain the following information:
9.1.2
Details on the operating procedures for electrical wireline logging in general. Details on the quality control requirements for specific log types. Details of the formats and layouts of logs.
Responsibilities
The Well Site Geologist / Petroleum engineer / Petrophysicist have the following responsibilities while logging: 9.1.3
Ensure all safety precautions have been taken Supervise operations Log quality control Supervise well site product delivery & distribution Ensure that reporting and follow up are completed Checks prior to logging
Prior to or during the pre-logging meeting, the Well Site geologist/Petroleum engineer / Petrophysicist should discuss the logging Programme in detail with the Operations Geologist or Petroleum Engineer. Discuss the logging Programme with the Logging Engineer to ensure he understands the log combinations required and the order that the tools will be run. The Programme should also be explained to the Drilling Supervisor and Drilling Engineer. Ensure that a second logging cable is on board as backup in order to prevent delays should fishing operations take place. Ensure that all the tools required for the job are on board and have been checked by the engineer well in advance of logging operations. Back up tools should also be checked (if available). Ensure that the Logging Engineer is provided with the following data: Field name, well number, location (geographical and UTM co-ordinates) water depth, RKB elevation. Logging Programme, level and run numbers. Drillers TD, hole size, size and depth of the last casing. Mud type and parameters, density, viscosity, chlorides, fluid loss, cake etc. Circulation time prior to POOH to log. Time when circulation stopped. Hole conditions (deviation, doglegs, tight spots etc.). Deviation survey records if TVD logs are required. Information on expected BHT and pressure. Details of rush prints, field prints and processed data required. Copies of logs from surrounding wells and the last logs run in the hole. Expected formation tops and hydrocarbon bearing intervals. Ensure that best practice is followed regarding pulling out of the hole prior to logging. If drilling with water based mud, a mud sample should be taken prior to stop of circulation.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 32 of 75
The mud Engineer should measure Rm, Rmf, Rmc and record the measured temperature of the sample. This temperature must not be derived from charts later. Ensure that the pre-job safety meeting has taken place with the drilling supervisor and tool pusher prior to logging to discuss the procedure and contingency plans for the logging operation. Advise the Logging Engineer of the depth control procedures to be used. Unless otherwise informed by the Operations Geologist on wireline conveyed operations the GR curve from the first logging run (up log) is to be used as the depth standard and that other logs must be tied in to it. 9.1.4
Pre-job planning meeting
To ensure a safely executed and smooth logging job pre-job planning is extremely important. There should have already been a pre-logging planning meeting held in town prior to every wireline logging operation. There should be a detailed logging programme generated from this meeting to compliment the logging programme within the drilling programme. The offshore pre-job meeting should be held at least 1 day prior to logging and be attended by a minimum of the logging engineers and the Well Site geologist/and or petroleum engineer, although presence of the drilling supervisor & tool pusher is recommended. In the case of drill pipe conveyed logging (TLC), pipe recovery, or through drill pipe operations the supervisor, tool pusher and driller must attend the meeting. In the planning meeting the following points should be addressed: § Discussion of current relevant geological and drilling issues § Discussion of safety issues § Radioactivity § Explosives (if in use). § Well control issues § Tool sticking § Rig up § Mud § Equipment lifts § Handling of equipments/tools § Status of logging company personnel on board § Status of logging equipment on board § Missing equipment § Preparation § Back-up § Problems § Finalisation of logging programme § Programme changes § Tool sketches and auxiliary equipment § Logging intervals / pressures points / stations / sidewall cores etc § Special procedures & equipment for difficult conditions § Review of past experiences from other wells § Data / product delivery & data transmission § Review of onshore planning meeting minutes § Review of contingency planning § Tool / pipe sticking § Tool not reaching TD § Lost circulation problems § Tool failures 9.1.5
Supervision of logging operation
When supervising the logging operation, the Well Site Geologist (and/or petroleum engineer when onsite) must ensure that the logging programme is carried out with a minimum of both down time (not directly attributable to the logging service company) & lost time (directly attributable to the logging service company).
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 33 of 75
By following the quality control procedures, the Well Site Geologist will ensure that the final product is as accurate as possible and meets Statoil’s standards. In certain cases Petrophysicist, reservoir engineers or geophysicists may be onsite to supervise key operations. If so they will be responsible for quality control of the applicable logs. 9.1.6
Real time Quality control
Application of an easy to remember method of real time quality control is important. Use the "ROCKS" method. The letters of ROCKS spell out the key principles of log quality control as follows: R - REPEATABILITY All logs should be checked for the quality of repeatability by running a repeat section and ensuring that it matches within a specified tolerance with the main pass. This should be displayed on the display as an overlay of the curves from the 2 passes. (Repeat analysis) O - OFFSET LOGS Logs made on nearby wells should always be available and compared with the logs being run. C - CALIBRATIONS All standard calibrations and checks should be made prior to logging, should be within tolerance and displayed on the log. K - KNOWN RESPONSE All logging tools give specific readings in specific conditions (for example a sonic tool should read 57 ms/ft in casing); these should be checked and displayed. In addition tool response should show specific expected trends in certain conditions (for example shallow resistivity should read lower than deep resistivity in a permeable oil zone drilled with water based mud). S - STANDARD OPERATING PROCEDURES The logging company’s standard operating procedures should always be followed. For example, correct logging speeds, correct stand-off or centralization, setting of parameters for environmental corrections etc. 9.1.7
Checks while logging
THE WELL SITE GEOLOGIST SHOULD BE IN THE LOGGING UNIT WHILE LOGGING. If a Petrophysicist or petroleum engineers is offshore he/she will witness the logging operation. Ensure that calibration procedures are carried out and that they are within the limits recommended by the logging company. Check the depth of the casing shoe and TD. Hole fill may reduce loggers TD compared to drillers TD. The stretch correction applied to the logging cable can sometimes cause loggers TD to be deeper than drillers TD. Ensure the various curves are on depth with each other. Depth tie in is by means of the GR. Ensure that sufficient overlap exists with previous runs to provide a clear tie in either through casing or in open hole. The repeat section (which should be at least 50m) is normally run from TD and up. Insist that the repeat is run over a section of hole showing contrasting log character and that the section is long enough to prove repeatability. When logging the reservoir, repeat sections should be run in the reservoir interval. If the hole is sticky, it may be better to make the main log first and then take the repeat section at the top of the logged interval. The neutron log can read through casing and can therefore be useful to tie in to previous runs. Continuously check the log on the monitor with a log from a near by well and/or the lithology for typical responses, formation tops and hydrocarbon intervals. Unusual log responses should be questioned. Check that porosity logs give the expected response in Salt or Anhydrite. Check that the resistivity and conductivity curves correspond. Watch for cycle skipping and noise on the sonic. If severe, run the tool at a slower speed or in extreme cases consider running it ex-centralized. Check for cyclic variations or sine wave patterns, especially on the S.P. curve. The occurrence of the latter may indicate a magnetized cable drum. Additional information on the logging operation or abnormal repairs should be explained in the remarks section. 9.1.8
Checks after Logging
Ensure that the log has good contrast, is clean and has no evidence of electrical interference. Check that before and after calibrations are attached to the 1:200 scale log and show no significant variation, that scales and curve coding are to Statoil requirements and attached to the top and bottom of the log. Check that the log is actually recorded
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 34 of 75
at the scale stated on the heading. Scales may be changed from standard if the bulk of the log runs along the edge of the log track, on and off backup. Check that: § Scale changes, intervals of anomalous response, baseline shifts, tool sticking points, total depth, casing points and back up curves are clearly labelled. § Curve coding is to Statoil standard. § The repeatability of logs. § The log is on depth with previous runs and that all curves are on depth with each other. At least 30 m of overlap has been recorded or that the GR, Neutron, Sonic and calliper have been recorded 30 m into the casing. § All details on the log heading have been filled out correctly, according to Link: Standard Operational Procedure (SOP). § The three BHT have been recorded with the circulation time before POOH and the elapsed time since circulation. § The Rm, Rmf, Rmc and temperature have been recorded.
§
9.1.9
Log Headings
Standard Scales and Codes In order to facilitate the use of logs it is required to have standardised coding (dots, dashes, lines etc.) for the various log display formats. These may be changed from time to time or may vary from area to area. The Well Site Geologist will ensure that these standards are followed by the different service companies employed on the rigs. It is equally important to use standard scales, 1:500 and 1:200, unless otherwise decided.
9.1.10 Log Numbering The log run number should always be displayed on the heading next to the log name. A system of numbering logs is applied in all operating areas. A number (starting with 1) represents a series of tools (suite) run at a particular level and this number is incremented every time the logging company rigs up at a NEW depth. A letter after the number (1A) represents the number of times a particular tool has been run successfully, starting with A and advancing each time the log is run. If a "Super combo" run is made which results in several different log prints being produced, especial care most be taken as in any well, successive logs of the same type must follow the sequence A, B, C, D.... without omission or repetition. Thus, while the level number for all the component logs of a super combo will necessarily be the same, the letter denoting number of times run will probably be different for the various logs. In this case, all the component letters should be reported whenever the super combo is concerned (e.g. AIT/DSI/LDL/CNL/NGL/SP 3C/B/A), whereas only the relevant letters are reported for the individual logs (e.g. AIT/DSI/GR/SP 3C, LDL/CNL/GR/CAL 3B, NGL 3A). Only log runs resulting in a log being produced and accepted should have a new letter. Misrun should be reported as such with the same letter until a good log is made.
9.1.11 Logging Service Bills & Invoices In order to ensure that wireline logging bills presented by the logging company at the well site are correctly filled in, these bills should be checked and signed by both the responsible Well Site Geologist and the Drilling Supervisor/Assistant Supervisor. Bearing in mind that these bills are often made at the end of a long logging job where errors can easily be made, it is very important that all items on the bill are checked thoroughly to ease later controlling of the bill when it gets into the Statoil system. The signing of the bill is to control that the work has in fact been carried out.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 35 of 75
9.1.12 Reporting Procedures (Logging Report) A logging report form should be filled out for each log run in the hole, successful or not, Link to Logging report form. Ensure that maximum recorded temperatures are reported. If these are not from TD, comment in the section for comments on Operations. Explain any lost time, tool failures, hole problems etc., in the same section. Any anomalous log response, intervals of poor log quality, cycle skipping etc. should be noted and explained in the section for comments on log quality. One copy of the Logging report should go into the Well site Geologists well file and a copy be sent to the Operations Geologist.
9.2 9.2.1
Borehole Seismic (VSP) Introduction
The Vertical Seismic Profile (VSP), also commonly known as borehole or well seismic, is a mature seismic method used to study near-well properties. The method differs from surface seismic because the sensors are placed down hole and the source can be either at the surface or down hole as well. Traditionally VSP surveys have been acquired to provide a vertical time-depth curve that helps tie 2D or 3D surface seismic data to seismic markers in the well. However, vertical time-depth curves are just one small example of the information a VSP survey can provide. Because VSP surveys use 3-component sensor array tools that are positioned at known depths in the well, VSP data are the best link between surface seismic and log data. This in turn connects reservoir properties to a real seismic response. Integrating VSP deliverables such as time-depth curves, calibrated velocity models, Pp, Ps, and shear wave images, and anisotropy parameters can significantly increase the value and confidence in existing and new reservoir models. 9.2.2
Responsibilities
The Well Site Geologist, Logging Engineer and/or a representative from Statoil’s VSP group will be responsible for the quality control of the Vertical Seismic Profiling (VSP) operations. Detailed information on operation procedures can be found in the best practice document: "VSP processing and sonic log calibration“. Relevant checklist for the VSP operation (“Offshore Guidelines”) can also be found on EaRTh Web (http://intranet.statoil.no/earthweb). The Well Site geologist shall: Ensure that the logging is performed according to the programme/given procedure delivered by the VSP group. Go through the logging programme with Logging contractor. Ensure that Logging contractor are provided with all necessary input data (final well position, final survey listing, GR log, final casing programme, if available, other useful logs, such as CBL etc. Be present when doing the first GR correlation (to decide what shift to use for tie in VSP depth with reference depth (from first logging run i.e.). Ensure that “Contractor’s field report” is distributed to Statoil VSP group asap.
The Statoil VSP group can be contacted if there are questions or problems during the operation, phone number will be listed in the VSP programme. The Operations Geologist and/or Logging Engineer on duty must be kept updated on the status of the VSP operation.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 36 of 75
9.2.3
Planning
The Well Project onshore will normally delegate the detailed VSP planning to the VSP group in Statoil. The Operations Geologist will be responsible for giving the special instructions and/or procedures to be followed during the VSP operations. If the operations are supervised by the VSP group, they are responsible for keeping the Operations Geologist and/or Logging Engineer on duty updated. The instructions will depend on which type of VSP to be performed. Check Shot: Measurement of the seismic travel time down to specific levels. All formation tops should be included in the list of defined levels. The source is hanging from the rig in a fixed position. Rig Source VSP: The source is hanging from the rig in a fixed position. Also sometimes referred to as Zero Offset VSP. Normal Incidence VSP: The source is hanging from a boat crane and positioned such that firing positions are vertically above the recording array for all levels. Fixed Offset VSP: The source is hanging from a boat crane. Source is positioned at a fixed location away from the rig. Walk-Away VSP: The source is towed by a boat, which moves along a given profile or profiles.
9.2.4
Before the survey (Before logging operation)
All the necessary equipment has to be checked to be working satisfactory. Noise from the rig and nearby boats should be minimized. The Drilling Supervisor and the Platform Manager should be informed in order to stop noisy work, both electrical and mechanical noise (welding, pumping etc.) during logging. The depth of the guns (Reference level = MSL) and the hydrophone has to be registered, and in addition, the distance and the direction from the well to the guns must be noted. All relevant information for the VSP operation shall be logged in the contractor’s field report. The Rotary Table (RKB) should be used as reference level for the depth measurement. The "zero point" shall be checked with the geophone hanging in the rotary table. This check has to be repeated after the logging operations, and differences larger than 2m should be reported to the Operations Geologist/VSP group immediately. If the VSP operations are performed in an open hole, remember to check the levels against the caliper log, especially in the rat-hole beneath the last casing shoe. Check if there are other disturbing seismic surveys in the nearby surroundings. Coordinating might then be necessary. 9.2.5
During the survey (The logging operation)
A checklist for the VSP operations can be found on the EaRTh Web. In addition a detailed checklist will also be included in the VSP logging programme (last page). When entering the hole, at least 2 RIH check-shots should be acquired to check the tool and at reflectors at known depths and seismic times. Details are given in the VSP logging programme/recommendations. The main logging operations will start at the deepest level (TD) and go on upwards. The check-shots performed on the way down shall be repeated when logging upwards, and should be in accordance to within +/- 2 ms. At each level the following should be checked:
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 37 of 75
At least 5 good readings shall be registered, and more if needed. A good reading will show up as a clear indisputable signal ("arrival") at the geophone. The first trough of the arrival signal gives the arrival time of the signal.
Unless otherwise specified in the VSP programme, the logging operation will normally end when the signal/noise ratio is unacceptably low and/or if the shape of the signal changes significantly. When entering multiple and/or poor cemented casing in vertical hole, the signal quality will normally deteriorate rapidly due to lack of acoustic coupling to the formation Above the 20" casing shoe, acceptable data are rarely obtained, due to casing signal arrivals. If more than one logging run is necessary (due to technical problems, look ahead a.o.), 7-9 levels from the first run(s) have to be shot again, in order to check repeatability of the tool and to be able to tie in the different parts. The Operations Geologist or the Logging Engineer should be notified if the VSP logging is terminated without fulfilling the planned programme. 9.2.6
After the survey (logging operation) - VSP data from the rig
The Well Site Geologist must assure that raw seismic data from the VSP acquisition along with the field report is transmitted onshore according to the VSP programme and logging instructions.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 38 of 75
10
Coring
10.1
Introduction
Core samples are valuable material from the wells, and they contribute to many of the analyses/interpretations to be performed. It is however, also the most time consuming and thereby the most expensive geological sampling. 10.2
The Well Site Geologist's responsibility concerning coring operation
The coring shall be in accordance with the NPD “Regulations relating to resource management in petroleum activities”, §9. Well specific information is given in the Drilling Operation Recommendation (DOR) and Drilling Operation Procedure (DOP). The Well Site Geologist shall keep the responsible Operations Geologist informed about well-related items that may obstruct or make the coring difficult and/or situations that may lead to coring in intervals not included in the Well Programme. Before starting the coring operations, the Well Site Geologist shall ascertain that the quality requirements are met with the mud (tritium added if required) and also that the coring operations are planned in a satisfactory way. It is also important that the coring is based on the requirements presented in the decision three for coring. The Well Site Geologist is responsible for: Registration and evaluation of all hydrocarbon shows and possible reservoir rocks, and in co-operation with the Operations Geologist decide if coring is necessary Decide and recommend the coring point(s) in accordance with the programme, and in co-operation with the Operations Geologist Keep close contact with the drilling-/coring personnel and give them information about expected lithology and experiences from previous wells. Make sure that the best procedures concerning core quality and core recovery and handling are followed Keep the Operations Geologist continuously updated on the status of the coring Ensure that all the equipment necessary for handling, marking, packing and transportation of the cores, are available on the rig Check that a proper area on the rig is ready for the core handling Ensure that the core(s) are treated with care and are not exposed to unnecessary damage Take the necessary/routine samples Ensure that correct measuring, labelling, sampling, description and preservation of the core(s) is done If core gamma will be run, ensure that the coring company perform core gamma when the core is laid out and marked on deck, prior to cutting Ensure that the core boxes are correctly marked and shipped at the first possible opportunity Ensure that a SJA (Safe Job Analysis) will be done on rig floor with both rig crews prior to handling of the core (drilling supervisor’s responsibility).
10.3
Methods used by Wellsite Geologist during coring operation
10.3.1 Coring programme The Coring programme will always be described in the Well Programme for the actual well. Check the DOR/DOP in addition to the coring decision tree.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 39 of 75
The programme usually consists of the following: In exploration wells at least one conventional core shall be taken from all zones containing hydrocarbons. Furthermore, necessary cores should be taken of potential source rock types and of reservoir rock types Conventional cores should be taken from the entire reservoir section in selected appraisal and development wells Coring should continue to at least below the water contact A decision three that tells when and where to start coring All non-conformances related to the Coring Programme shall be verified / discussed with the responsible Operations Geologist. Tritium tracer: Tritium might be added to the mud in front of the coring job, to be able to measure the invasion of mud into the cores. Ensure that the required tritium concentration is obtained before the core point is reached. A service company will take care of this operation. 10.3.2 Equipment for core handling Besides the ordinary coring equipment, the following equipment is necessary for a correct handling of the core (the equipment should be supplied by the coring company, the mud logging company and by Statoil): The well site geologists need to check that all relevant equipment is available Transport: The different coring companies and core laboratories can supply different kind of transport boxes. Statoil prefer the ResLab type. Transport boxes supported by ResLab are made as cubes with holes where the one meter-length core pieces are carefully placed. Corpro supply a similar type of transport boxes Transport boxes should be delivered in separate baskets for shipment. One extra basket for core shipments should be ordered, in order to prevent shipment in ordinary containers The core boxes have only one compartment and this should be made for 1m core pieces. Wooden boxes should only be used if aluminium boxes are not available! In some cases it should be considered to ship the cores onshore in 9 m lengths. Core marking/cutting: Red and black waterproof pencils are used for marking the inner barrels, red to the right. A core cutting saw with a spare saw blade. Support pieces for the inner barrel (at least 4 pieces). Chain tongs or pipe tongs to be used for removing the coring shoe, the end-caps, the lifting nipples etc.
Packing/sealing: lids and hose clamps for the inner barrels air powered screwdriver Other equipment: textile cloths for cleaning of inner barrels, hearing protection, dust masks, protection eye glasses, chisel, screw driver, geological hammer, tape measures (10 m and 2 m), sample bags and description sheets
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 40 of 75
10.3.3 Coring point decision If the geological models are well established, with reference wells in the vicinity of the current well, the coring interval will normally be decided prior to the start of the drilling. The coring point will in this case be given in the Well Programme. In areas with sparse geological information (e.g. in an exploration area), the exact coring point will be decided during drilling. The normal procedure for deciding the optimal coring point is to drill 3 to 5 metres into the formation/reservoir, after having registered a marked "drill break". The easiest way to be able to pick the optimal coring point is to keep all the drilling parameters as constant as possible. When use of MWD tool, gamma ray and resistivity logs can be used to pick the coring point if the tool reach into the reservoir. After having drilled into the formation to be cored, the bottom sample should be circulated out of the well for analysis. Positive signs are sand which gives fluorescence (oil or condensate) and/or a significant increase of the gas readings. Remember to check gas trap prior to circulating bottoms up. The Well Site Geologist shall contact the Operations Geologist prior to the coring operations and have his/hers confirmation for additional cores unless other agreements are made. 10.3.4 Coring operations The Well Site Geologist should work in close cooperation with the Coring Engineer, and thereby helping in the elimination of possible problems during the coring. Be aware that excessive filling up of the core barrels will result in possible core damage. When pulling the core out of the hole, it is important to be aware of the gas expansion, especially during the last 400 - 500 metres. It is mainly in this interval that the gas will expand, and a low pulling rate is therefore important in order to "bleed off" the pressure in a controlled way. This is especially important in situations with loose/unconsolidated formations, and in HPHT wells with low permeability reservoirs.
10.3.5 Tripping speeds The following recommendations for tripping speeds are based on numerous wells where no damage to the core has been observed. -
TD to 1600m 1600m to 400m 400m to 55m 55 m to surface
– 2 min / Stand – 3 min / Stand – 8 min / Stand – 10 min / Stand
The connection time is not included in the tripping speed. If gas is observed on the drill floor while braking down drill collar, reduce tripping speed. The normal sampling procedure for cuttings should be carried out throughout the cored interval, as a back up for a possible lost core. It should be remembered that the NPD requirements states a maximum of 3 metres between
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 41 of 75
each sample in the reservoir zone. Mud samples should also be collected when drilling through hydrocarbon bearing intervals. All necessary equipment for moving the core out of the drill floor, placing the core on a suitable place for cutting, for core description and packing should be ready in advance. It is of special importance to prepare for loose core pieces, mud samples, core chips etc. 10.3.6 Oriented cores When doing oriented coring, it is important to assure that the available knives are suitable for the formation. The scribe shoe holds the scribe knives. They are positioned in the ID of the shoe with unequal angles between each scribe knife. This identifies one of the knives as the reference knife. It is good practice to check the knife-marks on the recovered cores, for improvement related to smaller or larger knives, if the programme calls for several oriented cores. A certain survey tool is attached to the core barrel during the coring. It is very important that the Well Site Geologist immediately quality checks the survey data after each run and also transmit the data according to given procedures. 10.3.7 Handling of cores in the inner - barrel. The core should be kept in the inner-barrel. The core handling on the rig should be done as described below. If a complete description of the core is necessary, equipment for cutting a track in the inner-barrel may be considered used instead of taking the core out of the inner-barrel. The value of the information will usually not justify the possible damages on the core while taking it out of the barrel and putting it back in again. If, however, the core is taken out of the barrel it is of great importance to ascertain that the core pieces maintain their position and orientation while putting the core back in again. For safety reasons, only personnel needed for doing the job should be present at the working area while taking out the core and while cutting the core in 1 metre lengths. Personal safety equipment, ear protection, protection glasses, and the necessary permissions (for instance "hot work" permission and a Safe Job Analysis (SJA)), are mandatory for such work. 10.3.8 Core handling on the drill floor Before and during the opening of core barrels, checking for H 2S gas and hydrocarbon should be performed regularly. This is normally performed by the contractor. The different lengths of inner-barrels should be numbered before transported to the core handling area in a certified transport basket. Never transport or lift the inner barrels without transport basket. Before removing the core lengths from the drill floor, samples from the bottom of each length should be taken for description. This is of special importance if further coring/drilling operation is dependant on the information from the core (lithology and possible hydrocarbon shows). If possible, a mud sample from the inner-barrel should be collected, since this sample will be enriched by the formation liquid bled out of the core while pulling out of the hole.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 42 of 75
All core handling should be done in a way that makes as little damage as possible on the core, and it should be ascertained that the barrels are laid out in the correct succession. The practical way of doing this will, however, change from rig to rig. Only the personnel needed for doing the work should be present at the core handling area. 10.3.9 Marking The most important issue while marking the cores, is to make sure that no doubt concerning the up and down and the depth interval of each core exist when arriving at the laboratory. The inner-barrel should be cleaned and marked with waterproof pencils in red and black. The whole length of the barrel should be marked with to parallel lines, the red one to the right and the black one to the left when looking up the core from the bottom, i.e. "red to the right when looking upwards". Remember to put core pieces that have been out of the barrel, back in the correct place again.
2004
2004
2003
2003
The top of the core should be localized and the barrel should be cut at that point. The core will then be marked with the correct depth from the top and downward. The marking should be a short line and the depth values for each meter and at the end of the core barrel.
A list ("tally") should be made, in which the top and the bottom of each of the planned core lengths/core pieces are registered. Lost core material is supposed to be lost from the bottom, and the total length of the core is registered in percent of the cored interval. The utility-percent is calculated based on the total barrel length. The possibility of over pressured gas trapped in the inner-barrel, should never be forgotten, and it is important not to stand in front of the core ends while working on the core. This is especially important when using gel and in HPHT wells! 10.3.10Core Gamma A core gamma might be run after marking of the core has been done. The coring personnel will perform this job. It is important that the core gamma batteries are checked by the contractor in front of the operation. 10.3.11Core cutting Existence of a clearing between the core and the inner-barrel should be checked before any cutting action of the core starts. If no such clearing exists and in addition, trapped gas is suspected, holes should be drilled in the innerbarrel for ventilation unless ventilated tubes are used. Trapped gas in the inner-barrel may cause a dangerous situation while cutting the cores, as the core material may be expelled from the inner-barrel at a high speed. While sawing/cutting the core, a fat-pencil should primarily be used for greasing and cooling of the saw blade. The core/core barrel should never be exposed to water. The core shall always be cut at exact every meter mark. NB- use eye, ear and breathing protection when sawing the core into meter lengths.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 43 of 75
10.3.12Sampling and core description During the handling of the core, from drill floor until it is placed in the core box, it is important to look for and to register damage on the core, such as washouts, sticking and/or crushing. Link: Best practice core descriptions.
in case of jamming of the core, it is important to record the actual depth interval. any correction of the core length will be based on observations from the previous core/core results. samples should be collected from all the cuts and from the top and the bottom of the core. the Mud Logging Engineers shall collect cuttings as usual during coring if cuttings are available. 10.3.13Packing of cores
If the core does not fill up all of the space in the inner-barrel, the "empty space" shall be stuffed for instance with textile rugs in a plastic bag or with other suitable materials. The textile must not have direct contact with the core. The inner-barrel should be sealed in both ends by plastic lids and tube clamps. The lids shall be marked with core number and depth. Loose core pieces should be packed in plastic bags or in a suitable length of inner-barrel. It is important that no doubt about up/down and depth exist. The core is packed/transported in special core boxes. The core must be stabilized in the boxes. Information such as the well number, the core number, top / bottom and from/to depths for the core pieces shall be stored inside the core transport boxes. The only information outside the transport boxes is the well-, core- and box numbers and the total number of boxes, (e.g. box no. 2 of 19). 10.3.14Shipment of cores The transport core boxes shall be placed in the special containers in which the boxes were delivered and then be shipped to the core handling company onshore at the first possible opportunity. Avoid loading and transport in very bad weather. It is required that the transport containers have shock log sensors activated during transport from the rig to the laboratory. In winter time it is required to use containers with heating to avoid freezing of the core (Arctic climatic areas). In most situations the core boxes will be delivered in full baskets, which have the effect that not enough baskets will be available if the coring goes on for a long time and cores are shipped onshore in half filled baskets. It is therefore important to have some extra baskets on the rig. If the core boxes for some reason have to be shipped by helicopter, the crane operator and other involved personnel should be contacted in advance. A 1 metre 4" core in a box has a weight of approx. 30 kilos and 1 metre 5 1/2" core will have a weight of 50 kilos. Since the cores may be fragile, such boxes should be handled in a controlled way. "Handle with care" tags should be considered, especially when unconsolidated core material are shipped ashore. A dispatch note with well- and core number, and also the total number of boxes, has to be prepared. A detailed packing list with the content of each box and with to/from depths, shall be enclosed with the dispatch note. The dispatch note may be placed in one of the core boxes which then will be marked "Dispatch note inside", or it may be forwarded by putting it in an envelope with the receivers address and sending it together with the other papers from the rig. On the "cargo manifest" no details are required, only the number of boxes and a notification that they contains "core samples" or "geological material".
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 44 of 75
10.4
Gel filled inner-barrels
This coring method, in which the core will displace a gel material in the inner-barrel, will minimize the contact between the mud and the core. It may possibly also have a "greasing" effect that thereby may reduce the possibility of getting stuck while coring (jamming). The gel is supposed to be in a liquid state while influenced by the pressure and temperature conditions in the well, but in a viscous state at the rig. In principle the handling of cores in gel-filled inner-barrels are as for other cores, but due to the gel, situations in which the pressure is not properly "bled off" have been experienced. This may cause problems while measuring, marking and dividing the cores, since the cores may expand/float inside the inner-barrels and thereby create empty intervals between the core pieces. In such situations it is impossible to measure and mark the core before it is cut. The normal practice has been to mark the top of the core with correct depth and thereafter measuring/marking the inner-barrel/"core" according to normal procedure, but without the depth marks and instead using the "core number" together with the top/bottom of piece 1, 2, 3, and so on. The final measurements have been done onshore. An alternative way of doing this is to ship the core onshore in 9 metres lengths. The advantage with this procedure is that the core is less exposed for damages, the disadvantage however, is that less of the core is exposed for inspection. As described above, gel filled core barrels may cause some extra work compared to ordinary cores. The use of gel in HPHT wells with low permeability reservoirs will increase the above-mentioned problems. 10.5
Handling of unconsolidated core material
Several techniques exist: injection of gypsum, resin, exposure in dry ice and injection of foam. In some of these techniques the core material is moulded in an either gypsum or epoxy material inside the core barrel. The coring/laboratory company will perform the preservation work on the rig. 10.6
Special analyses, sealed core ("seal peal")
Specific procedures/sampling programme connected to special studies, such as saturation measurements, wetting preferences etc., will be included in the coring programme. The service companies will have personnel on the rig to perform such special studies, to use tracer in the mud and to drill out, pack and ship core plugs for such purposes. When using inner-barrels, special sealing procedures will usually not be necessary. Experience shows that the normal sealing of the inner-barrel is sufficient. If necessary, samples for a special sealing on the rig (seal peals), may be required. Special guidelines will then be given. (15 cm seal peal/1 m sand section) If rock mechanical studies are required parts of the core that contains shale will be stored in base oil.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 45 of 75
11
Sidewall coring
11.1
Introduction
The Well Site Geologist shall ascertain that sampling of sidewall cores is performed according to the programme and the mandatory and guiding documents for logging.
11.2
Objectives
The objectives of acquiring sidewall cores may be several, the following included: Geochemistry (source rock evaluation) Biostratigraphy Lithology (correlating to wireline logs or for reservoir purposes) Por. / perm measurements Other (requirements from the licence partners, the NPD etc.) The objectives will be listed in the Well Program, and depending of these, the levels for sidewall cores have to be carefully considered 11.2.1 Wellsite Geology procecures for depth control during sidewall coring The depth control will often be a critical parameter for the results of the coring, for instance in thin coal layers. The following procedures should be used: The GR should be used for the depth correlation The depth correlation should be as accurate as possible, preferably within 20cm. The GR log should be the same as the one used for picking the MSCT depths If "working" the string, thereby causing tension in the cable, is necessary in order to get the tool free, the depth correlation should be checked on a regular basis Sidewall core recovery/collection The Well Site Geologist shall supervise the sampling of the sidewall cores when they are coming out of the hole, in order to make sure that they are placed in the correct succession The samples shall be delivered from the logging company in a glass container (marked with the core number on the container lid and with well number, core number and depth on the glass itself) and placed in special boxes 11.2.2 Depths for sidewall cores
The SWC depths will refer to the wireline log depths. Based on the instructions from the Operations Geologist, a list containing depths, hole size, expected lithology and hardness (dt) will be prepared. The calliper log shall always be checked, due to the limited range of the equipment. Four-armed calliper (from dip meter i.e.) shall be used when available. If it is necessary to take sidewall cores in the reservoir, equipment for drilling out the cores in unconsolidated formations must be evaluated 11.3
Operational routines
Normally a MSCT tool is used for sidewall coring. But if CST tool is used; according to the logging company's routines radio silence will be required due to use of explosives.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 46 of 75
.
The deepest samples shall be acquired first
11.4
Use of sidewall cores
11.4.1 Geochemistry
Gamma Ray, Resistivity, Density and Calliper logs should be used in scale 1:200. The samples should be acquired either in shale or in coal formations Shale samples should be taken from intervals in which the GR has high values and the resistivity has relatively high readings (dark organic-rich shale). Coal samples should be taken from intervals with low GR readings, high resistivity and low density (less than 1.80 g/cc) readings. Samples has to be acquired from more than one coal layer in the same interval 11.4.2 Biostratigraphy
Gamma Ray (Spectralog), Resistivity and Calliper logs should be used in scale 1:200. The samples should be acquired from shale formations (if possible above and below formation/ Biostratigraphical boundaries), in intervals with the highest GR and the lowest resistivity readings. Usually this will be from the lower parts of the shale. If spectralog is available the Th/U/K relation may be used for deciding the clay type and thereby give an indication of the depositional environment, for instance whether marine shale or other shale’s are present. 11.4.3 Lithology
Sandstones are most relevant Gamma Ray and Calliper logs should be used in scale 1:200 Clean sandstones ( low GR) with a reasonable good porosity should be used, and intervals with thick mud cakes should be avoided. At least two samples from each sand unit should be acquired if possible.
11.5
Sidewall Core Equipment
The details of the equipment to be used, shall be discussed with the Logging Engineer (based on lithology/ formation hardness/sonic log, area experience etc.) For Conventional sidewall cores the MSCT (Mechanical Sidewall Coring Tool) will be used. For drilled sidewall cores it is important that the correct type of bits, length and diameter are used A complete equipment list can be furnished by the logging engineer 11.5.1 Reporting
The recovery of the sidewall coring should be reported under the logging section in the daily drilling report, in the Sidewall Coring Report form (Link Sidewall Coring Report form) and may also be reported in the remarks field of the geology section. The report should contain all sidewall cores planned, number of lost cores, number of empty cartridges, the number of accepted cores and core length The information should be reported in the Section Report The Well Site Geologist will decide which cores to be accepted. If the recovery is low, the Operations Geologist should be consulted for discussion and decision of having another run or not. Even in hard formations the cores should be at least 10 mm long in order to be accepted. The sidewall cores shall be registered on the Composite Log, and it is important that they are depth corrected according to the actual log. The logging company shall prepare a summary which shows the depth correlations, sample depths and the results (rec./lost/empty).
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 47 of 75
11.6
Description
See Chapter 3.3.4 “Sidewall core descriptions” for general information. The description has do be done based on a fresh fracture surface, free of mud/filtrate. A sharp knife may be used if necessary The core should be fully described and tested for hydrocarbons. Excess mud should be wiped form the core and any large structures noted. Care should be taken to avoid damaging or contaminating of the core and the microscopic examination should be performed on a small chip taken from the end of the core away from the well bore. The cores shall be measured and the length should be reported in millimetres. The uppermost (shallowest) core is to be described first, and similar descriptions can be repeated for the succeeding cores. It is mandatory to minimize the damage done to the cores. At depths where cores are missing, the reason for this should be noted (“type of lithology”, or “empty”) or tool failure. The description of the cores will be recorded on the sidewall core description sheet using standard abbreviations. The description sheet heading must be filled out. All SWC description sheets will be sent to the Operations office concerned as a standard routine. 11.7
Packing, marking and shipment
Samples will be sent from the rig by the first available helicopter addressed to the Operations Geologist or various service laboratories (biostrath. geochem. etc.) as outlined in the Sample Handling and Distribution instructions for each well. The Operations Geologist will give instructions on which samples should go to each laboratory, if needed. The cores shall be carefully packed in aluminium sheets and thereafter be placed in the above mentioned glass containers. The sample must be stable in the glasses. The glasses should be shipped in boxes constructed for the purpose and furnished by the logging company. Cores taken for por. / perm measurements shall be packed in air tight packaging as soon as possible. Suitable packaging will be supplied by the Operations Geologist/laboratory onshore. The air must be taken out of the packages before they are sealed with heat. The core descriptions can be reduced, if necessary, to avoid unnecessary air exposure. alternative packing in order to avoid moisture loss from the core or moisture from outside to enter the core: a) The core should be wrapped in plastic foil (Glad pack) to seal the sample off from air exposure. Make sure that no air pockets exist against the core. b) Put the core into a plastic bag, evacuate all air by tightening the bag around the core and seal off with tape to prevent any moisture from entering c) Place the core in a suitable plastic container supplied with screw cap d) Wrap slightly water moistened paper around the sample as shock absorbent. Make sure that no excess water is present. e) Tighten the lid to ensure that plastic container is air/water tight
The core should be addressed to the Operations Geologist, unless otherwise is agreed. A manifest should be included inside each box A copy of this manifest should be given to the Operations Geologist with the addition of the address to which the samples were sent. A copy of the Sample description sheet may also be included.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 48 of 75
12
Other services
12.1
Introduction
In order to fulfil the responsibility for geological data acquisition and data quality, it is important to be acquainted with the different services available in the market, for instance geochemistry services (GHM, OSA i.e.), FLAIR (gas analysis) and onsite Biostratigraphy. For this reason it is important that sufficient background documentation (e.g. quality control manuals) are available on the rig/platform (onsite). Concerning coring, sidewall coring, VSP and wireline logging, reference is made to the respective chapters in this document and in the task documents for wireline logging and MWD/LWD. Other procedures for acquiring, reporting and shipping data shall be agreed with the Operations Geologist in each specific case. The service companies report shall be based on observations and registrations performed with their own equipment. They are obliged to relate to Statoil's requirements for securing data when handling Statoil's data. 12.2
Wellsite Geology Requirements concerning other services
The Wellsite Geologist shall; -
-
The service companies should at any time have enough and competent personnel on the rig. The companies are also obliged to appoint a dedicated contact person ("unit manager"), and to prepare a list of the personnel planned for the specific job. If, for some reason, it is necessary to use personnel that are not on this list, Statoil shall be informed in advance, also about the reason for the change. Ensure that sufficient back ground information is available ensure that the data collected by the companies are reported according to best practise.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 49 of 75
12.3
Forms for reporting
Link to all forms with examples in appendix: Standard sample description form Caving description form Conventional Core Description Core Summary sheet Core chip description Core description sheet from Winlog Logging report form Sidewall Core Description sheet Sidewall Coring Report form Summary of lithological descriptions (XL-file) Risk log Cross-section DBR; Daily, Section report, Experience report Geological Morning Report NPD report/Shallow gas report Evaluation of service companies Detailed logging operation report The Geology Qualification scheme should be used for this purpose
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 50 of 75
App A
Lithological Description
A.1
Introduction
The lithological description must be carried out as objective as possible, and in an orderly manner. Continuity of quality and form is required between Geologists working on different shifts and on various rigs. Cuttings, rock pieces from cores and sidewall cores shall be examined by use of a microscope while they are wet, and the description shall be in accordance with the following "Procedure for rock description". The rock descriptions shall be carried out on the Statoil standard sample description sheet. Standard word abbreviations shall be used (see Appendix D). A.2
Procedure for rock description
The rock properties should be described in a given sequence and should be applied to all rock types. An uniform basic approach has certain advantages: 1) Ensures all important properties are recorded. 2) Increases uniformity of description among Well Site Geologists. 3) Reduces problems in obtaining specific information from description. For fine clastic sediments the grain size will not be described and for limestone the crystal size will be described instead of the grain size. By excluding some properties, which are not relevant for a given lithology, the mentioned standard, given below, may be used for most lithology.
Rock name Modified rock name Colour Dominant mineralogy Texture Grain - /Crystal size Physical Texture Grain - /Crystal shape Sorting Matrix Cementing Hardness Structures (sedimentary and diagenetic) Fossils Porosity and permeability Hydrocarbon indications Pollution Other relevant parameters
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 51 of 75
A.2.1 Rock names Definitions of ordinary rock types: Conglomerate/gravel: A clastic sediment comprising grains/fragments with a diameter greater than 2mm. Sand/sandstone: A clastic sediment comprising grains/fragments with diameter in the range 2 - 0.063mm. Silt/siltstone: A clastic sediment comprising grains/fragments with diameter in the range 0.063 - 0.004mm. Clay: A clastic sediment comprising grains/fragments with diameter less than 0.004mm. Claystone: Petrified clay without stratification and cleavage Shale: Petrified clay with stratification and cleavage Chert (Flint): Hard and extremely tight and compact cryptocrystalline sedimentary rock comprising mainly cryptocrystalline silica and minor amounts of micro- and cryptocrystalline quartz and amorphous silica. The fracture surfaces are smooth and concoidale. Limestone: Sedimentary carbonate rock containing more than 50% CaCO 3, which means the minerals calcite or/and aragonite. Chalk: A limestone created of calcium remnants from pelagic organisms. Dolomite: A sedimentary carbonate rock containing more than 50% of the mineral dolomite or a limestone that is rich in magnesium-carbonate. Marl: Consists of 40-60% limestone/dolomite mud and 60-40% clay. The term marl should be used for rocks with low grade of consolidation. Consolidated rocks are designated as limestone with clay content or as claystone with a lime content, depending on the composition. Lignite/coal: The carbon content comprises more than 50% of the rock. Tuff: Contains more than 50% volcanic ashes. Anhydrite: Calcium phosphate, CaSO4, exists with different crystal forms, usually relatively coarse crystalline and either clear, white or greyish. Gypsum: Calcium sulphate with crystalline water, CaSo42H2O. Consist of usually clear and coarse crystals. Salt: Halite, usually clear. A.2.2 Modified rock names If the rock, besides the main lithology, contains other prominent elements, either related to the texture or to the composition, and these elements constitute at least 20% of the rock, they shall be described as modified rock
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 52 of 75
names. If the content is less than 20%, the elements will be classified as other components (see chapter B.2.13 in this Appendix). opal chalcedony microgranular quartz
calsium carbonate limestone
siliceous limestone
limestone
50
50
50
claystone argillaceous sandstone
sandy claystone
claystone clay
sand
When describing limestone it should be classified (modified) according to Dunham (1962), Classification of Carbonate Rocks according to Depositional Texture (p.108-121) CLASSIFICATION ACCORDING TO DEPOSITIONAL TEXTURE Recognizable depositional texture Original components not bound together during deposition Contains mud (particles of clay and fine silt size) Mud supported
Lacks mud
Grain supported
Less than 10% grains
More than 10% grains
Mud present between grains
Lacs mud, clean grains
Mudstone Slamstein (Mdst)
Wackestone Vakkestein (Wkst)
Packstone Pakkestein (Pkst)
Grainstone Kornstein (Grst)
Original components bound together during deposition as shown by intergrown skeletal matter, lamination contrary to gravity, or sedimentfloored cavities that are roofed over by organic or questionably organic matter and too large to interstices.
Boundstone Festestein (Bdst)
Irrecognizable depositional texture
Classification by means of physical texture or diagenesis
Crystalline carbonate Krystallinsk karbonat Xln (Dol/Ls)
(Modified after Dunham 1962)
Reference is also made to Folk (1954) Classification of siliclastic rocks (NPD-Bulletin No. 7, Geostandard - A geological standard for use within the petroleum industry). Different mineralogical modification are also permitted, for instance "... calcareous, dolomitic, micaceous....". A.2.3 Colour The rock colour shall be described by using the ROCK-COLOUR CHART, distributed by the GEOLOGICAL SOCIETY OF AMERICA P.O. Box 9140 Boulder, CO 80401, USA.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 53 of 75
The colour should be described while the samples are wet, in uniform blue light and at the lowest magnification on the microscope. It is of importance to view the sample and the Rock-colour chart under identical lighting conditions. Individual cuttings can be placed beside the coloured blocks in the chart book and viewed under the microscope. Avoid placing the sample directly on the coloured block as this leads to smearing of mud and sample which masks or changes the original colour. Variations in rock colours may be described as: Laminated (laminert); the colours appears in regular alternating thin bands. Banded (båndet); the colours appears in nearly parallel lines Streaked (stripet); for elongated colour lenses. Variegated (broket); two or more colours in a non-systematic mixture. Spotted (flekket); More or less symmetrical medium size spots of one colour, scattered around in a matrix of another colour. Speckled (spettet); a colour scattered around as small speckles in a matrix of another colour. Varicoloured (flerfarget); tree or more colours with clear boundaries. Mottled (spraglet); two or more colours with indistinct and irregular boundaries. Ambiguous terms such as "buff" and "tan" should be avoided. A.2.4 Dominant Mineralogy
This should describe the main mineral constituent of the rock in the case of non- carbonate clastic i.e. quartz, and the main clastic component in the case of carbonate clastic i.e. calc arenite. A.2.5 Texture A.2.5.1
Grain-/Crystal size
The grain size should be decided by using a grain size model. Siliciclastic rocks
Grain/crystal size (mm)
Boulder (blokk) Cobble (stein) Pebble (småstein) Granule (grus) Very coarse sand Coarse sand Medium sand Fine sand Very fine sand Silt Clay
> - 256 64 - 256 4 - 64 2-4 1-2 0,5 - 1 0.25 – 0.5 0.125 – 0.25 0.063 – 0.125 0.004 – 0.063 < 0.004
A.2.5.2
Carbonate rocks/crystal size very coarse krystalline mega crystalline very coarse crystalline coarse crystalline medium crystalline fine crystalline very fine crystalline microcrystalline cryptocrystalline
Physical Texture
Grains can be denoted as: Vitreous (glassaktig) Frosted (matte) Pitted (korrodert) Coated (belagt)
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 54 of 75
Clay and shale can be: Amorphous (strukturløs) Waxy (voksaktig) Earthy (jordaktig) A.2.5.3
Grain - /crystal shape
The shape of the grains can give valuable information about the depositional history of the rock. Two components shall be described: 1. Roundness: Describes the grade of sharpness of the grain edges. The evaluation is done by a visual comparison between the grain and a reference chart (Fig. B.1). 2. Sphericity: Describes the shape of a grain compared to a ball. The evaluation is done by a visual comparison between the grain and a reference chart (Fig. B.1). A.2.6
Sorting
The sorting of the grains gives a measure of the grain size variation in the sediment. The evaluation is done by a visual comparison by using a reference chart (Fig. B.1). The type of sorting, e.g. bimodal should also be mentioned. A.2.7 Matrix The matrix of sediment is the mechanical deposited fine material between the rock grains, and it will influence porosity and permeability. Silt and clay are the most usual matrix materials. Since it is impossible to differentiate between the different clay types in the matrix (kaolin, illite etc.) by use of the equipment available on the rig, the matrix is only supposed to be described by its colour, for instance "wh cly mtx". The amount of matrix is estimated as abundant to rare. A.2.8 Cementing Cement is a term applied to authigenic grain coating and pore filling material. It is an important characteristic of any potential reservoir as it affects both porosity and permeability. The most common cement minerals are silica, calcite, dolomite and siderite. Both the amount and the type of cement shall be described.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 55 of 75
Very well sorted
Well sorted
Moderately sorted
Poorly sorted
Very poorly sorted
Classification of degrees of sorting as seen through a square hand lens. Silt- and clay- sized sediments are indicated by fine stipple. Figure B.1.
Classification: Internal
Roundness, sphericality, sorting
Status: Final
Expiry date: 2011-02-04
Page 56 of 75
A.2.9 Hardness The samples should be tested for hardness by a steel needle. The hardness is referenced to the aggregations of minerals more than to the specific grains and crystals. The following qualitative terms may be used: Loose, the grains are separated Friable (smuldrende), the grains stick together but crumble easily between the fingers Soft, the rock is easily broken/deformed Firm, the rock may be broken by the fingers Moderate hard, specific grains may be loosened by a steel needle, it is possible to break the rock Hard, impossible to loosen specific grains, cracks between the grains, it is difficult to break the rock Very hard, the rock will crack across the grains. An example is quartzite Other expressions used in connection with compaction/hardening of sediments are: Unconsolidated Plastic, used about clay, easy deformable Sticky (klebrig), sticks to a steel needle and to fingers Brittle (sprø), used about coal, easily splintered A.2.10 Cleavage The term cleavage is used in the description of fine-grained sediments (silt/clay). Rock cleavage or fissility in fine clastic is also a process of mechanical compaction and Rearrangement of grains and the degree of fissility should be described. The following explanations are used: Massive, no cleavage Blocky, cleavage across the layering Sub fissile (delvis spaltbar), cleavage sub parallel to the layering Fissile (spaltbar), cleavage parallel to the layering Splintery (splintrig), parallel and sub parallel cleavage A.2.11 Structures Sedimentary and diagenetic structures will be described below. Only minor structures are detectable in the cuttings material, and usually it is necessary to have cores or sidewall cores available in order to describe structures in a rock. Both solely descriptive expressions, such as “graded layering", and interpretative expressions, such as "stream flutes", may be used. An example of a diagenetic structure may be stylolites. Reference is made to the NPD Bulletin no.7, Geostandard - A geological standard for use within the petroleum industry, for details of different structures. A.2.12 Other components Components that constitute only a minor part of the rock volume (< 20%), may however be of importance for the interpretation of the depositional environment, and also in correlation work. The most usual components will typically be different minerals such as mica, glauconitic, pyrite etc., and fossils, lithic fragments and plant remnants. The calcium content of fine clastic rocks is supposed to be described in this context.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 57 of 75
A.2.13 Other characteristics Some rocks, especially clay, will react to contact with water and may therefore be described as: Soluble, disperses easily in water Swelling, special types of breakage shall also be described, e.g. concoidale breaks in coal. A.2.14 Porosity and permeability The porosity is defined as the empty space in a rock. Both the amount and the type of porosity shall be described, and dried cuttings shall be used for the porosity evaluation. Since this will be a visual evaluation, the amount of porosity has to be given by use of qualitative expressions, according to the following: No visual porosity porosity not seen Poor visual porosity 5 - 10% Fair visual porosity 10 - 15% Good visual porosity 15 - 20% Excellent visual porosity > 20% Different types of porosity must also be described (if possible i.e. when thin sections are available): Inter granular, porosity between individual grains or rock fragments Intra granular, porosity within the individual grains or rock fragments Inter crystalline, porosity between the individual crystals (often in dolomite) Vugg, more or less irregular cavities Cracks, due to mechanical deformation A.3
Percentage
It is difficult to quantify the percentage of the different rocks. By use of "percentage chart", (Fig. B.2, next page) it is however, possible to give a relative distribution of the different rock types. It is sufficient to give the percentage to the nearest 5%. In addition, the following expressions are used for recording fossils, minerals and other elements, as a percentage of the whole sample: Abundant 10 - 20% Trace 1 - 10% Rare > 1% Some expressions do also have a qualitative element and are used to describe repetitive lithological series: Alternating: two main rock types, each comprising between 40% and 60% of the series. Interbedded: two main rock types of which one of them constitutes between 20% and 40%. Minor: one rock type that constitutes between 10% and 20%. Trace: one rock type which constitutes >10%
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 58 of 75
1%
2%
3%
5%
7%
10%
15%
20%
25%
30%
40%
50%
Figure B.2 Percentage chart
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 59 of 75
A.4
Other relevant advice
After a duty relief the previous samples have to be checked in order to maintain continuity and regularity in the descriptions. By complying to the standard for lithological descriptions given above, the variations should not be to pronounced. Minor variations of different qualities, especially colour, may be easier to detect if several samples are placed together for comparison (multi viewing). The shape of the cuttings is influenced by several factors, including; the type of drill bit used, the use of turbine, whether the formation reacts to the mud and whether it is a highly deviated well. This must be considered during the evaluation and the description. The cuttings should be checked on the shakers before being described. Minor, but important variations in hardness, stickiness, sand content, caving and other matters may then be detected. Different portions of the sample should be examined. This may give a hint of the amount of caving, amongst other items. The cementing will also be easier described by examining bigger fragments. Be aware of caving, and make sure that they are not included in the recorded amount of material. The caving condition should be described under the remarks section. Be also aware of mud additives that may look like minerals/rock types from the drilled formation. Examples of this may be lignite (coal), LCM material, barite and gypsum.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 60 of 75
App B
Wellsite Geology responsibilities concerning Hydrocarbon Shows
The Well Site Geologist shall, without delay, inform the Drilling Supervisor about any registrations of hydrocarbons. All samples shall be analysed under UV light in order to detect possible fluorescence, and every hydrocarbon indications shall be evaluated and reported according to the prevailing routines. Accurate descriptions of hydrocarbon indications ("shows") can be of conclusive significance, and as such should be regarded as one of the most important tasks for the Well Site Geologist. Reference is made to table C.1 in order to obtain a qualitative description of the hydrocarbon shows, as uniform as possible. After the analyses, the Well Site Geologist should to be able to give an interpretation of which type of hydrocarbons are present. B.1
Registration of hydrocarbons
The registration of hydrocarbons is a continuous process. The different possible registrations are:
Ditch gas (background gas, gas peaks, trip gas, connection gas etc) Cuttings /blender gas Oil in the mud Hydrocarbon odour Oil stain and leaking of oil Fluorescent samples Dissolved hydrocarbons and fluorescence
B.2
Gas readings
B.2.1
Ditch gas
Ditch gas is created during drilling and is registered as background gas. The amount of gas is directly connected to "the amount of drilled rock pr. time unit". Increasing gas readings are therefore natural if the drilling rate is increasing. The gas readings will also increase while drilling through gas rich and/or permeable formations. The amount of gas will be influenced by the mud weight, and it is registered by burning the gas in a gas detector. Two types of gas detectors are available; a total gas detector and a gas chromatograph (In some cases the Flair gas system will be used in advance). The total gas detector will burn all of the gas and register it as C 1-equivalents. The gas chromatograph register the gases C1, C2, C3, nC4, iC4, nC5 and iC5, and the results are given in Parts Per Million (ppm). If nC4 and iC 4 are present, the Well Site Geologist has to ascertain that possible presence of nC5 and iC 5 is checked and measured on a regular basis. The Flair gas system detects gas up to C 8. Two types of degassers for separating the gas from the mud are used.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 61 of 75
1. The standard degasser is partially submerged in the mudflow, normally in the header box (shaker box). It releases the gas from the mud flowing through by means of an agitator. The gas is trapped above the mud level in a confined space that also has an outlet to air. The mud level in the header box, the amount of mud flowing through the trap and the position where it is installed in the header box affect the degasser. In addition the degassing is not very efficient, releasing mainly the light components, and will therefore give a biased picture of the gas composition in the reservoir. The newer models of this trap are installed so they are floating in the mud, thereby attempting to minimize the effect of varying mud levels. This type of gas trap is supported by all mud logging companies. 2. Geoservices have developed a "constant volume degasser", which pumps up a constant volume of mud per unit time through a flexible sampling hose. This hose can easily be positioned optimally to the mudflow. This degasser is much more independent of mudflow and mud level in the shaker box. Tests have shown that it is also much more effective releasing the heavy components from the mud, thus giving a more correct picture of the gas composition in the reservoir. FID (Flame Ionizing Detector) used for chromatography analyses is now standard equipment by all mud companies. Other available detectors are only used as an assurance in the case of FID chromatograph failure. The improved new system, "Reserval", is more accurate and has a full cycle analysis (C 1 - nC5) within 50 seconds. The system with the standard degasser gives higher readings than the "constant volume degasser". The difference in gas readings is small in concentrations lower than 1%, but increases to 5-10 times in higher gas concentrations. The standards degas machine overestimates the C1 concentration and underestimates heavier components. When comparing gas concentrations with other wells, it is important to know which method has been used. This should also be considered when using ratio plots/diagrams for evaluating the type of reservoir liquid. These plots/diagrams are usually empirical and based on data acquired by a standard degas machine. Measurements from systems with the constant volume degas machine, if available, should be preferred due to greater accuracy, and measurements from systems with standard degas machine should be used as back-up. During drilling it should be differentiated between: Background gas during drilling Maximum gas during drilling Connection gas Trip gas All of these four gas types are registered in relation to the zero line in the gas detector. The gas types shall be reported every day, as a percentage and with the related chromatograph reading.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 62 of 75
B.2.2
Cuttings gas
The registration of cuttings gas can give valuable support to the interpretation and the description of hydrocarbons. Approximately 100 grams of unwashed cuttings should be whipped in a mixer and the released gas should be registered either in a total gas detector or in a gas chromatograph. Significantly higher gas readings in the cuttings than registered as total gas, may indicate drilling through a reservoir with low permeability. B.2.3
Gas Ratio Analysis
The Gas Ratio Analysis can give valuable information/indications concerning the maturation and the reservoir potential. Ratio plots for evaluation of the reservoir liquid should primarily be based on constant volume measurements, if available. The different mud logging companies will use their own methods, but they are usually based on the same principles. Exlog's "Mud logging, Principles and Interpretations" gives a good introduction to the principles of Gas Ratio Analysis. The other companies have corresponding documentation. These analyses should be used if heavier (nC4 etc.) are present. Link: Gas Oil Ratio Analysis B.2.4
Oil in the mud
Oil may be washed out of the cuttings by the mud, and may be registered as a dark film on the mud. The mud should then be examined under UV light, and the possible colour and intensity of the fluorescence be described. It is important to ascertain that no chemicals that may react to the UV light, are used in the mud.
B.3
Shows descriptions
B.3.1
Hydrocarbon odour
The odour of hydrocarbons is usually only detectable on new fracture planes in cores, and rarely from the cuttings. The odour is described as follows: None Weak Fair Good Strong
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 63 of 75
B.3.2
Oil stain
Oil stain is detectable on cores and cuttings when the sample is examined in a microscope with normal light. The content of oil in the sample is dependant of the rate of washing while transporting the sample by the mud. This reflects the rate of permeability, and a relatively tight rock may show good oil stains. Such zones must be registered. The rate of oil stain is a function of porosity and distribution of oil in the pores. The colour of the stain will give information concerning the oil density, that is, heavy oil will have a dark colour and lighter oils will be more and more colourless. The oil colour shall be reported by: The amount The distribution (spotted, even) The colour The amount of oil colour will qualitatively be reported as: excellent, 90-100% evenly distributed good, 50-90% evenly distributed fair, 20-50% spotted/evenly distributed poor, 10-20% spotted trace, < 10% spotted B.3.3
Natural fluorescence
All samples shall be examined for fluorescence under UV light. In order to have as representative analyses on the core samples as possible, the samples should be collected from "non flushed" material. If necessary the samples have to be taken from the middle of the core. The natural fluorescence from fresh, dry or wet samples shall be registered. It is important to distinguish between hydrocarbon fluorescence and mineral fluorescence. Some ordinary minerals such as dolomite and feldspar typically will have yellow or yellow-green fluorescence, and anhydrite has blue-grey fluorescence. The minerals, possibly also the fossil fragments, will not give cut fluorescence when adding solvent. In such cases no detectable hydrocarbons shall be reported. The mineral fluorescence shall not be described, reported or drawn on the logs. In addition to mineral fluorescence, mud chemicals and greasing materials may also give fluorescence, for instance the so called "pipe dope", which gives blue-white fluorescence. As soon as fluorescence is detected, the previous samples shall be rechecked in order to ascertain that no hydrocarbons have been overlooked.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 64 of 75
The hydrocarbon fluorescence shall be described by: Distribution Intensity Colour Amount The distribution of fluorescence shall be described as: Even Mottled/patchy Spotted Pinpoint The intensity of the fluorescence should be recorded as: Dull Pale Moderate Strong/bright The colours to be used are: Approximate hydrocarbon density none 3
violet blue-white yellow-white green-white
0.785 g/cm
gas
whitish yellow
0.83-0.785 g/cm
yellow yellow-orange gold
0.88-0.83 g/cm
3
orange brown-orange
0.94-0.91 g/cm
3
brown
0.94 g/cm
condensate
3
3
light oil "Brent" oil
heavy/bitumen oil
The amount should be qualitatively reported, see chapter C.1.6. B.3.4
Cut fluorescence
Within all intervals in which hydrocarbons are suspected, the samples shall be checked for streaming fluorescence. Representative rock fragments that give fluorescence should be taken out and dried for some minutes before adding the dissolving agent. The reason for this is that the water film on a wet sample may prevent the dissolution material to have contact with possible hydrocarbons. The sample should be observed under UV light. The time of reaction, the type of dissolution, the fluorescence colour and possibly also the colour of the dried dissolution should be described. Different types of dissolution fluids are used, mostly Isopropyl Alcohol (IPA), but all of them evaporate easily and should not be inhaled. They should all be handled with care. Trichlorethane is no longer allowed, and is hence not longer used as dissolution material. (Trichlorethane might change to nerve gas if exposed to heat and UV light)
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 65 of 75
AVOID SPILL ON THE SKIN AND INHALING THE EVAPORATED LIQUID. Due to the possible health risk, samples that have been added such dissolution material should not be stored unless ventilated in a proper way. The samples should be destroyed as soon as they are described. The time of reaction should be described as: None Slow Moderate Fast Instantaneous The dissolution pattern should be described as: Flash Cloudy/blooming Streaming Ring If a sample does not show streaming fluorescence it should be broken and observed again. Colour and intensity should be described as listed in chapter C.1.7 Notice that different dissolving agents will act different and give different colours. Therefore the dissolving agent should be noted together with the description of the cut fluorescence. B.3.5
Residual dissolution(dried)
The intensity of the dissolution pattern should be described as: excellent, 90-100% evenly distributed good, 50-90% evenly distributed fair, 20-50% spotted/evenly distributed poor, 10-20% spotted trace, < 10% spotted
The dissolution pattern should be described as: Spotted Cloudy/blooming Even Ring During the evaporation process toxic gases may be released, and due to this fact the UV-box shall always be connected to a proper ventilation device.
B.3.6
Hydrocarbon shows in oil based mud
Due to the background fluorescence that sometimes exists, description of hydrocarbon shows may be more difficult in oil-based mud than in water-based mud. The base oil dissolved natural HC very good compared to water; hence there is often not much to see in cuttings. In unflushed part of cores, virgin HC shows can be observed.
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 66 of 75
The background fluorescence usually has a characteristic pale yellow-green colour, and with some experience it might be possible to separate it from the base oil fluorescence. Exlog's "Logging Techniques in Oil Based Drilling Fluids", 1984, gives a detailed description of techniques related to hydrocarbon shows in oil based mud. B.4
Hydrocarbon show evaluation
The shows evaluation depends on the rock porosity, type of fluorescence and the percentage of rock-pieces with shows as given in Table C.1 below.
PERCENT OF FORMATION WITH SHOWS
POOR OR NO POROSITY, LITTLE OR NO STAIN, WEAK FLUORESCENCE, CRUSHING CUT
FAIR VIS POROSITY, FAIR VIS. STAIN, MODERATE FLUORESCENCE SLOW STREAMING CUT
GOOD POROSITY GOOD VISIBLE STAIN, BRIGHT FLUORESCENCE GOOD STREAMING CUT
FEW PIECES TO 10%
TRACE
POOR
POOR - FAIR
POOR
FAIR
FAIR - GOOD
FAIR
GOOD
GOOD - EXCELLENT
GOOD
EXCELLENT
EXCELLENT
10 - 20% 25 - 50% GREATER THAN 50%
Table C.1 Qualitative evaluation of registered hydrocarbons
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 67 of 75
App C
Abbreviations for Lithological Descriptions Note:
Classification: Internal
Abbreviations for nouns always begin with a capital letter.
Status: Final
Expiry date: 2011-02-04
Page 68 of 75
WORD
ABBREVIATION
A about
abt
above absent abundant acicular agglomerate aggregate algae, algal allochem altered alternating ammonite amorphous amount and angular anhedral anhydrite (-ic) anthracite aphanitic apparent appears approximate aragonite arenaceous argillaceous arkose (-ic) as above asphalt (ic) assemblage associated at authigenic average
ab abs abd acic Aglm Agg Alg, alg Allo alt altg Amm amor amt & ang ahd Anhy, anhy Anthr aph apr ap apprx Arag aren arg Ark, ark a.a. Asph, asph Assem assoc @ authg Av, av
B background band (-ed) barite basalt (-ic) base basement become (-ing) bed (-ed) bedding bentonite (-ic) bioclastic bioherm (-al) biomicrite bimodal biosparite WORD
bkgrd Bnd, bnd Bar Bas, bas bse Bm bcm Bd, bd Bdg Bent, bent biocl Bioh, bioh Biomi bimod Biosp ABBREVIATION
biostrom (-al) biotite bioturbated bird’s-eye bitumen (-ious)
Biost, biost Biot bioturb Bdeye Bit, bit
Classification: Internal
Status: Final
black (-ish) blade (-ed) bleeding blocky blooming blue (-ish) bored (-ing) bottom botryoid (-al) boulder boundstone brachiopod brackish branching break breccia (-ted) bright brittle brown bryozoa bubble buff burrow (-ed)
blk, blksh Bld, bld bldg blky blmg bl, blsh Bor, bor Btm Bot, bot Bld Bdst Brach brak brhg Brk, brk Brec, brec brt brit brn Bry Bubl bu Bur, bur
C calcarenite calcilutite calcirudite calcisiltite calcisphere calcite (-ic) calcareous caliche carbonaceous carbonized cavern (-ous) caving cement (-ed, -ing) cephalopod chalcedony (-ic) chalk (-y) charophyte chert (-y) chitin (-ous) chlorite (-ic) chocolate circulate (-ion) WORD
Clcar Clclt Clcrd Clslt Clcsp Calc, calctc calc cche carb cb Cav, cav Cvg Cmt, cmt Ceph Chal, chal Chk, chky Char Cht, cht Chit, chit Chlor, chlor choc circ, Circ ABBREVIATION
clastic clay (-ey) claystone clean clear cleavage cloudy cluster coal coarse coarsening upwards coated (-ing) coated grains
clas Cl, cl Clst cln clr Clvg cldy Clus c crs CU cotd, cotg, Cotg cotd gr
Expiry date: 2011-02-04
Page 69 of 75
cobble colour (-ed) common compact compare concentric conchoidal concretion (-ary) conglomerate (-ic) conodont considerable consolidated conspicuous contact contamination (-ed) content contorted coquina (-oid) coral, coralline core covered cream crenulated crinkled crinoid (-al) cross cross-bedded cross-laminated cross-stratified crumbly crumpled crush cryptocrystalline ,crystal (-line) cube, cubic cuttings
Cbl col, col com cpct cf cncn conch Conc, conc Cgl, cgl Cono cons consol conspic Ctc Contam, contam Cont cntrt Coq, coqid Cor, corln C, cov crm cren crnk Crin, crinal x x-bd x-lam x-strat crmb crpld crsh crpxln Xl, xln Cub, cub Ctgs
D dark (-er) dead debris decrease (-ing) deformed dense depauperate WORD
dk, dkr dd Deb Decr, decr def dns depau ABBREVIATION
deposited description detrital devitrified diabase diagenesis (-etic) diameter difference direct discontinous disseminated distillate ditto dolomite (-ic) dominant (-ly)
dep Descr detr devit Db Diagn, diagn Dia dif dir discon dissem Dist " or do Dol, dol dom
Classification: Internal
Status: Final
downward (-s) drilling drill stem test drusy dull
dwrd drlg DST dru dll
E earthy east echinoid elevation elongate embedded equant equivalent euhedral euxinic evaporite (-itic) excellent exposed extraclast (-ic) estimate extremely extrusive rock extrusive
ea E Ech Elev elong embd eqnt Equiv euhd eux Evap, evap ex exp Exclas, exclas est extr Exv exv
F facet (-ed) faint fair fault (-ed) fauna feet feldspar (-athic) fenestra (-al) ferruginous fibrous fine (-ly) firm fissile fissure (s) fining upwards flaggy WORD
Fac, fac fnt fr Flt, flt Fau Ft Fspr, fspr Fen, fen ferr fibr f, fnly frm fis fiss FU flg ABBREVIATION
flake, flaky flaser flat floating flora fluorescence (-ent) foliated foot foraminifer, foraminiferal formation fossil (-iferous) fracture (-d) fragment (-al) frequent fresh friable fringe (-ing)
Flk, flk flsr fl fltg Flo Fluor, fluor fol Ft Foram, foram Fm Foss, foss Frac, frac Frag, frag freq frs fri Frg, frg
Expiry date: 2011-02-04
Page 70 of 75
frosted frosted quartz grains fucoid (-al) fusulinid
fros F.Q.G. Fuc, fuc Fus
G gabbro gastropod gas generally geopetal gilsonite glass (-y) glauconite (-itic) Globigerina (-inal) gloss (-y) gneiss (-ic) good grading grain (-s, -ed) grainstone granite granite wash granule (-ar) grapestone graptolite gravel grey, grey (-ish) graywacke greasy green (-ish) grit (-ty) gypsum (-iferous)
Gab Gast G gen gept Gil Glas, glas Glauc, glauc Glob, glob Glos, glos Gns, gns gd grad Gr, gr Grst Grt G.W. Gran, gran grapst Grap Grv gry, grysh Gwke gsy gn, gnsh Gt, gt Gyp, gyp
H hackly halite (-iferous) hard heavy hematite (-ic) Heterostegina WORD
hkl Hal, hal hd hvy Hem, hem Het ABBREVIATION
heterogeneous high (-ly) homogeneous horizontal hydrocarbon hygroscopic
hetr hi hom hor Hydc hyg
I igneous rock (igneous) immediate impression inch inclusion (-ded) increasing indistinct indurated Inoceramus. in part insoluble
Ig, ig imm Imp In Incl, incl incr indst ind Inoc i.p. insl
Classification: Internal
Status: Final
instant (-eous) interbedded intercalated intercrystalline intergranular intergrown interlaminated interparticle intersticies (-itial) interval intraclast (-ic) intraparticle intrusive rock, intrusive invertebrate iridescent ironstone irregular (-ly) isopachous
inst intbd intercal intxln intgran intgn intrlam intpar Intst, intst Intvl Intclas, intclas intrapar Intr, intr Invtb irid Fe-st irr iso
J jasper joint (-ed, -ing)
Jasp Jt, jt
K kaolin (-itic)
Kao, kao
L lacustrine lamina (-tions, -ated) large laterite (-itic) lavender layer leached lens, lenticular light lignite (-itic) limestone limonite (itic) WORD
lac Lam, lam lge Lat, lat lav Lyr lchd Len, lent lt Lig, lig Ls Lim, lim ABBREVIATION
limy lithic lithographic lithology (-ic) little littoral local long loose lower lustre lutite
lmy lit lithgr Lith, lith Ltl litt loc lg lse 1 Lstr Lut
M macrofossil magnetite, magnetic manganese.mangan(fer) marble marl (-y) marlstone marine
Macrofos Mag, mag Mn, mn Mbl Mrl, mrl Mrlst marn
Expiry date: 2011-02-04
Page 71 of 75
maroon massive material matrix maximum medium member meniscus metamorphic rock, metamorphic (-osed) mica (-ceous) micrite (-ic) microcrystalline microfossil (-iferous) microfos micrograined micro-oolite micropore (-osity) micropor microspar microstylolite middle miliolid milky mineral (-ized) minor moderate mold (-ic) mollusc mosaic mottled mud (-dy) mudstone muscovite
mar mass Mat Mtrx max m or med. Mbr men Meta meta, metaph Mic, mic Micr, micr microxln Microfos, micgr Microol Micropor, Microspr Microstyl Mid Milid mky Min, min mnr mod Mol, mol Moll mos mott md, mdy Mdst Musc
N nacreous nodules (-ar) normal
nac Nod, nod nrm
WORD
ABBREVIATION
north no sample no show novaculite no visible porosity numerous
N n.s. n/s Novac n.v.p. num
O occasional ochre odour oil oil source rock olive ooid (-al) oolicast (-ic) oolite (-itic) oomold (-ic) oncolite (-oidal)
occ och od O OSR olv OO, oo Ooc, ooc Ool, 00l Oomol, oomol Onc, onc
Classification: Internal
Status: Final
opaque orange (-ish) Orbitolina organic orthoclase orthoquartzite ostracod overgrowth oxidised oyster
op or, orsh Orbit org Orth O-Qtz Ostr ovgth ox Oyst
P packstone pale paper (-y) part (-ly) particle parting parts per million patch (-y) pebble (-ly) pelecypod pellet (-al) pelletoid (-al) permeability (-able) pendular (-ous) petroleum, petroliferous phlogopite phosphate (-atic) phyllite, phyllitic phreatic pink pinkish pin-point (porosity) pisoid (~al) pisolite, pisolitic pitted plagioclase WORD
Pkst pa Pap, pap Pt, pt Par, par Ptg PPM Pch, pch Pbl, pbl Pelec Pel, pel Peld, peld Perm, k, perm Pend, pend Pet, pet Phlog Phos, phos Phyl, phyl phr pk pkish P-PPiso, piso Pisol, pisol pit Plag ABBREVIATION
planar plant plastic platy polish, polished pollen polygonal polymict (-ic) poor porcelaneous porosity, porous possible (-ly) predominant (-ly) preserved primary probable (-ly) production prominent pseudopseudo oolite (-ic) pumice-stone purple
pln Plt plas plty Pol, pol Poln poly polmc pr porcel Por, , por poss pred pres prim prob Prod prom ps Psool, psool Pst purp
Expiry date: 2011-02-04
Page 72 of 75
pyrite (-itized, -itic) pyrobitumen pyroclastic
Pyr, pyr Pybit pyrcl
Q quartz (-ose) quartzite (-ic)
Qtz, qtz Qtzt, qtzt
R radial (-ating) radiaxial range rare recemented recovery (-ered) recrystallized red (-ish) reef (-oid) remains replaced (-ment) reservoir residue (-ual) resinous rhomb (-ic) ripple rock round (-ed) rounded, frosted, pitted rubble (-bly) rudist
Rad, rad Radax rng r recem Rec, rec rexlzd rd, rdsh Rf, rf Rem rep, Repl resv Res, res rsns Rhb, rhb Rpl Rk rnd, rndd r.f.p. Rbl, rbl Rud
S saccharoidal salt (-y) salt and pepper salt water WORD
sacc Sa, sa s&p S.W. ABBREVIATION
same as above sample sand (-y) sandstone saturation (-ated) scarce scattered schist (-ose) scolecodont secondary sediment (-ary) selenite shale (-ly) Shell shelter porosity show siderite (-itic) sidewall core silica (-iceous) silky silt (-y) siltstone similar skeletal
a.a. Spl Sd, sdy Sst Sat, sat scs scat Sch, sch Scol sec Sed, sed Sel Sh, sh Shl Shlt por Shw Sid, sid S.W.C. Sil, sil slky Slt, slty Sltst sim skel
Classification: Internal
Status: Final
slabby slate (-y) slickenside (-d) slight (-ly) slow slumped small smooth soft solution, soluble somewhat sorted (-ing) south spar (-ry) sparse (-ly) speck (-led) sphalerite spherule (-itic) spicule (-ar) splintery sponge spore spotted (-y) stain (-ed, -ing) stalactitic sticky strata (-ified) streak (-ed) streaming striae (-ted) stringer stromatolite (-itic) stromatoporoid strong WORD
slb Sl, sl Slick, slick sli, slily slo slmp sml sm sft Sol, sol smwt srt, srtg s Spr, spr sps, spsly Spk, spkld Sphal Spher, spher Spic, spic Splin spg Spo sptd, spty Stn, stn stal stky Strat, strat Strk, strk strmg Stri, stri strgr Stromlt, stromlt Strom strg ABBREVIATION
structure stylolite (-itic) subangular subelongate subfissile sublithic subrounded sucrosic sulphur, sulphurous superficial oolite (-ic) surface syntaxial
Str Styl, styl sbang sbelg sbfis sblit sbrndd suc Su, su Spfool, spfool Surf syn
T tabular (-ate) tan terriginous texture (-d) thick thin thin-bedded thin section throughout tight top tough
tab tn ter Tex, tex thk thn t.b. T.S. thru ti Tp tgh
Expiry date: 2011-02-04
Page 73 of 75
trace translucent transparent trilobite tripoli (-itic) tube (-ular) tuff (-aceous) type (-ical)
Tr trnsl trnsp Tril Trip, trip Tub, tub Tf, tf Typ, typ
U unconformity unconsolidated underclay underlying uniform upper upwards
Unconf uncons Uc undly uni u uwrd
V vadose variation (able) variegated varicoloured varved vein (-ing, -ed) veinlet vermillon vertebrate vertical very very poor sample vesicular WORD
Vad, vad Var, var vgt varic vrvd Vn, vn Vnlet verm vrtb vert v V.P.S. ves ABBREVIATION
violet visible vitreous (-ified) volatile volcanic rock, volcanic vug (-gy)
vi vis vit volat Volc, volc Vug, vug
W wackestone washed residue water wavy waxy weak weathered well west white with without wood
Wkst W.R. Wtr wvy wxy wk wthd Wl, wl w wh w/ w/o Wd
Y yellow (ish)
yel, yelsh
Z zircon zone
Zr Zn
Classification: Internal
App D
Status: Final
Expiry date: 2011-02-04
Page 74 of 75
References Statoil’s requirements and local authority requirements (APOS) Directional Drilling requirements - Link Theme document Wireline logging- Link Theme document MWD/LWD- Link Theme document Geosteering- Link Theme document pore pressure- Link Theme document DST - Link Theme document Operations geology Link Theme document Geological and petroleum technical data Acquisition Usable references: Mud Logging Handbook (Whittaker) Log Data Acquisition and Quality Control (Theys)
Statoil Winlog User Guide
Geological interpretation of well logs (M.Rider). Well Site Geology Course Documentation http://npd.no Link: Standard Operational Procedures (SOP). (http://intranet.statoil.no/earthweb). Link: Best practice core descriptions Lithology Coding for Open Works Standard forms: Link to core chips description sheet. Link to Statoil’s Well Site sample descr_form Link to sidewall core description sheet. Link to The Geology Qualification scheme should be used for this purpose Gas Oil Ratio Analysis
Classification: Internal
Status: Final
Expiry date: 2011-02-04
Page 75 of 75
Related Documents
Manual Wellsite Geology
February 2021 0
Wellsite Geology Manual Omv
February 2021 0
Geology The Wellsite Guide
January 2021 1
Manual Of Field Geology
January 2021 2
Geology
February 2021 3
Wellsite Geologist S Guide
January 2021 0More Documents from "Prasanti Plaban Dash"