Reservoir-simulation-fs

Reservoir Simulation& Numerical Simulators

Khaled FEKI 2019 K.FEKI

1

Course Objectives…

 Learn about reservoir simulation using ECLIPSE Blackoil.  Understand how the simulator initializes and executes.  Define corner point grid geometry.  Describe rock and fluid properties.  Allocate initial pressure and saturation distributions.  Define aquifers.  Control wells under history matching and prediction.

K.FEKI

2

LECTURE TOPICS  Introduction  Data preparation  Gridding  Upscaling  Fluid description  Initialisation  Aquifer representation  Wells representations  History matching  Prediction  Numerical simulator :Eclipse  Petrel  Eclipse/Petrel worshop K.FEKI

3

Course Objectives…  Lecture: • Introduction to simulation • Introduction to ECLIPSE • ECLIPSE model: Discuss each section of the data file. • Convergence issues  Exercises: • Build a model from scratch. • Use Petrel to compare results.

K.FEKI

4

THE CHALLENGE OF RESERVOIR SIMULATION …

K.FEKI

5

DYNAMIC RESERVOIR SIMULATION

K.FEKI

6

Incentives for running a flow simulation

K.FEKI

7

Reservoir Simulation Basics



The reservoir is divided into many cells.



Basic data is provided for each cell.



Wells are positioned within the cells.



The required well production rates are specified as a function of time.



The equations are solved to give the pressure and saturations for each block as well as the production of each phase from each well.

K.FEKI

8

Simulating Flow 

Flow from one grid block to the next



Flow from a grid block to the well completion



Flow within the wells (and surface networks). Flow = Transmissibility * Mobility * Potential Difference

Geometry and Properties

Fluid Properties

K.FEKI

Well Productio n 9

Reservoir simulator

K.FEKI

10

Reservoir simulation model

K.FEKI

11

Reservoir simulation model

K.FEKI

12

Main modeled phenomena

K.FEKI

13

Definitions

K.FEKI

14

Types of models

K.FEKI

15

Types of simulators

K.FEKI

16

Types of simulators

K.FEKI

17

Black Oil model

K.FEKI

18

NUMERICAL MODELS: DISCRETIZATION

K.FEKI

19

Reservoir Simulation PLANNING

K.FEKI

20

Prediction Future performance Reservoir Simulation Model

Geological Model

History Matching

Reduce Operation Expenses Increase Recovery

K.FEKI

Prediction

21

Problem definition

K.FEKI

22

Data review

K.FEKI

23

Main Types of Data

K.FEKI

24

Study approach

K.FEKI

25

Study approach

K.FEKI

26

Gridding

K.FEKI

27

GRID TYPES

K.FEKI

28

GRID TYPES

Cartesian

Corner Point

Block-Centered

Unstructured (PEBI)

Radial

K.FEKI

29

Sugar box geometry \ Block-Centered

K.FEKI

30

Sugar box geometry \ Block-Centered

K.FEKI

31

Block-centered grid

K.FEKI

32

Block-centered grid

K.FEKI

33

Block-centered grid

K.FEKI

34

Dip or fault ?

K.FEKI

35

Corner point geometry

K.FEKI

36

CPG grid intercell flow

K.FEKI

37

Fault description in CPG grid

K.FEKI

38

Example of CPG reservoir model

K.FEKI

39

Block-Centered vs. Corner Point: Geometry

K.FEKI

40

Block-Centered vs. Corner Point: Geometry

Block-Centered:

Corner Point: – Cell description can be complex. – Pre-processor is required. – Geometry data is voluminous. – Geologic structures can be modelled accurately. – Pinchouts and unconformities can be modelled accurately. – Layer contiguity across fault planes is accurately modelled.

– Cell description is simple. – Pre-processor is not required. – Geometry data is small. – Geologic structures are modelled simplistically. – Pinchouts and unconformities are difficult to model. – Incorrect cell connections across faults (user must modify transmissibility).

K.FEKI

41

Reservoir description : PROPERTIES

K.FEKI

42

Reservoir description : PROPERTIES

K.FEKI

43

Cartesian Data Reading Convention

Cell data is read with i cycling fastest, followed by j, then k.

K.FEKI

44

Cartesian Data Reading Convention Cell data is read with R cycling fastest, followed by , then k.

K.FEKI

45

Block Identification and Ordering • • • •

Natural ordering Zebra ordering Diagonal D2 ordering Alternating diagonal D4 ordering • Cycle ordering • Cycle-2 ordering

K.FEKI

46

ACTIVE and DEAD CELLS

K.FEKI

47

NUMBER OF GRID CELLS

K.FEKI

48

GRID ORIENTATION

K.FEKI

49

CHOICE OF VERTICAL DISCRETIZATION

K.FEKI

50

Using LGR to model gas coning

K.FEKI

51

Grid definition: Quiz

K.FEKI

52

Reservoir layering

K.FEKI

53

Reservoir layering: Use of log Correlation

K.FEKI

54

Reservoir layering: Quiz

K.FEKI

55

Upscaling

• Optimum level of and techniques for upscaling to minimize errors

Gurpinar, 2001

K.FEKI

56

Rock properties: Main parameters

K.FEKI

57

Rock properties: Net thickness and porosity

K.FEKI

58

Rock properties: Compressibility

K.FEKI

59

Rock properties: Compressibility

K.FEKI

60

Horizontal & Vertical Permeability

K.FEKI

61

Horizontal Permeability

K.FEKI

62

Vertical Permeability

K.FEKI

63

Fluid description

K.FEKI

64

Fluid description: Influence of reservoir temperature

K.FEKI

65

Fluid description: Black oil assumptions

K.FEKI

66

Fluid description: Black oil relationships

K.FEKI

67

Fluid description: Black oil representation

K.FEKI

68

Black oil: From surface to reservoir conditions

K.FEKI

69

Fluid description: PVT Regions

K.FEKI

70

Initial state : Summary

K.FEKI

71

Initial state : Pressure calculations

K.FEKI

72

Example of the initial reservoir condition calculations

K.FEKI

73

Computing the initial pressure distribution

K.FEKI

74

Computing the initial pressure distribution

K.FEKI

75

Initial state: Saturation calculation

K.FEKI

76

Initial state: Water-Oil contact definition

K.FEKI

77

Initial state: Saturation calculation

78

Initial state: Saturation Height function

79

Initial state: Water-Oil contact discretization

80

Aquifer Representation

81

Aquifer Representation

82

Use of large grid cells

83

Van Everdingen and Hurst approach

84

Van Everdingen and Hurst approach

85

Van Everdingen and Hurst

86

Van Everdingen and Hurst approach

87

Van Everdingen and Hurst approach

88

Wells’ representation

K.FEKI

89

Wells representation

K.FEKI

90

Wells representation: Inflow performance

K.FEKI

91

Wells representation: Inflow performance

K.FEKI

92

HISTORY MATCHING OBJECTIVE Validate (Calibrate) the reservoir characterization by comparing performance of the model with historical performance (rates, pressures, saturations) PRINCIPLE Reproduce with the model the measured evolutions of pressure, BSW and GOR by well, by zone or for the entire field. Difficulties Uncertainties on fault and flow barriers network.

 RULE OF THUMB Predictions are reliable on a period twice the production period.

93

HISTORY MATCHING: Main issues  Observed flows are imposed on wells during the history period.  One expect to reproduce:  pressure evolution  WOR and GOR  WOC and GOC contacts  This is not a simple work as:  Many data are unknown (no information is available far from wells)  It is not obvious to detect the most influent data (all data act together)  Some artefacts must be corrected (grid size, grid orientation,…)  It is possible to distinguish between two main types of problems:  Pressure match  Saturation match 94

Steps IN HISTORY MATCHING STEP 1 : Identification of available data that have to be matched • Adapt data to grid size STEP 2 : Data Analysis • Identification of main uncertainty in the Geomodel STEP 3 : Selection of matching parameters • Identification of probable range for each matching parameter STEP 4 : Modification of matching parameters • Trial and error process  G&G must work hard to help the reservoir engineer to maintain the consistency of the geological model, It is better to have rough, consistent matching than matching which is accurate but destroys the model.  It is better to have rough, consistent matching than matching which is accurate but destroys the model.

95

History Matching

K.FEKI

96

History matching: Data to match  Determine the accuracy and frequency of measurements • Which kind of separator (Gas-Liquid, 3 phase separator) • How is measured WOR, GOR if no 3 phase separator? • Frequency of measurements (weekly, monthly?) • Activity factor (% of activity of the wells)  Allocation of rates to perforated interval • Completion and well status (casing, cement) to be known • Production logging is the best tool to allocate rate • If no production logging, estimate the accuracy of allocation to intervals • When possible, draw the maps of injected fluid breakthrough for each Interval  Shut-in pressures of wells • look at pressure curves to estimate the pressure in the cell 97

History matching: Data to match  RFT in wells drilled after the start of production • Differential depletion by interval • Communication through faults  Observation wells • Shut-in wells should be changed to observation wells  WHP of wells not usually used • Flow in tubing difficult to match exactly, interference with surface flow lines

98

History matching strategy First Phase: pressure match  Look at total fluid production and average pressure (kind of material balance): • Of the whole field • Of parts of the field (compartments, or zones determined from the geological analysis, layers)  Change first the more uncertain parameters by zone • Aquifer transmissibility (kh) , storativity (kh ct), • Reservoir permeability o Multiplying factor to reproduce pressure gradients o Vertical connections to account for pressure discrepancies between layers (RFT useful) o Connections through faults to account for different pressure regimes 99

Pressure match : Material balance Objective • Get a correct evolution with time of the average reservoir pressure  Main parameters • Volumes Originally in Place • Aquifer size & water influx • Pore & Fluid Compressibility  Important notice • The material balance should address the whole reservoir voidage (no material balance per fluid in surface conditions) • It is useful to get an energy balance to have an estimation of the importance of each individual production mechanisms (pore volume contraction, fluid expansion, water sweep, gas sweep …)

K.FEKI

100

Pressure match : Material balance

Reservoir voidage calculation:

Q res = Qo . Bo (P) + {Qg - Rs (P) . Qo (P)}. Bg (P) + Qw . Bw (P)  Important notice • Reservoir voidage has to be calculated and is depending on the reservoir pressure. • ECLIPSE keyword for reservoir voidage is RESV.

K.FEKI

101

Pressure match : Darcy’ law

Objective • Get a correct geometry of the flow lines and pressure drop along flow lines Main parameters o One phase flow • Transmissivity distribution o Multi phase flow • Transmissivity distribution • Transfer functions (relative permeability & capillary pressure).

K.FEKI

102

Pressure match : Diffusivity equation

Objective • Get a correct evolution of reservoir pressure versus time and space. Diffusivity equation:

Main parameters:

K.FEKI

103

Numerical production indices PEACEMAN formula

K.FEKI

104

History matching strategy Second step: Fluid distribution matching  By zones (compartments, or zones determined from the geological analysis, layers) look at contacts movements, WOR and GOR of wells. Try to match fluid BT (breakthrough), fluid produced volumes.  Adjust first the permeability distribution

• Vertical distribution by layer and connection between layers (vertical permeability) • Areal distribution of permeability (barriers, high permeability zones, sealing or conductive faults)  change Kr only if changes in permeability distribution cannot achieve a satisfactory match • First check if initial water saturation is correctly represented

105

History matching strategy Final step: well by well match

 Once the global and zonal matches are correct, look at each well  Check if the cell size is not the cause of an incorrect match  Check if coning can be suspected and is not taken into account By specific well Kr functions  Check if the discrepancy does not reveal a completion problem(cement or casing leak, fluid entry from another interval)  Corrections should remain in the vicinity of the well

106

FIRST STEP - GENERAL FIELD MATCH - RUN 1

K.FEKI

107

FIRST STEP - GENERAL FIELD MATCH - RUN 1

K.FEKI

108

FINAL STEP - GENERAL FIELD MATCH - RUN 3

K.FEKI

109

History matching : Some advices Flow directions are not correct if pressure is not matched • Don’t try to match saturations if you are not matched in pressure

 Early well behaviour correspond to area close to the wells • Concentrate on well data to match early production times  Late well behaviour correspond to area far from the wells • Don’t limit your analysis close to the wells to match late production times  Modification of matching parameters • Try to anticipate model reactions by using simple calculations • Don’t introduce new parameters without a look back to G&G

K.FEKI

110

History matching : Some advices Flow directions are not correct if pressure is not matched • Don’t try to match saturations if you are not matched in pressure

 Early well behaviour correspond to area close to the wells • Concentrate on well data to match early production times  Late well behaviour correspond to area far from the wells • Don’t limit your analysis close to the wells to match late production times  Modification of matching parameters • Try to anticipate model reactions by using simple calculations • Don’t introduce new parameters without a look back to G&G

K.FEKI

111

NUMERICAL SIMULATOR (ECLIPSE)  ECLIPSE 100 is a three phases, three dimensional, general purpose black

oil simulator with gas condensate option.  Program is written in FORTRAN77 and operate on any computer with an

ANSI-standard FORTRAN77 compiler and with sufficient memory.  ECLIPSE 100 can be used to simulate 1, 2 or 3 phase systems. Two phase

options (oil/water, oil/gas, gas/water) are solved as two component systems saving both computer storage and computer time. In addition to gas dissolving in oil (variable bubble point pressure or gas/oil ratio), ECLIPSE 100 may also be used to model oil vaporizing in gas (variable dew point pressure or oil/gas ratio).  Both corner-point and conventional block-center geometry options are

available in ECLIPSE. Radial and Cartesian block-center options are available in 1, 2 or 3 dimensions. A 3D radial option completes the circle allowing flow to take place across the 0/360 degree interface. New Names for the ECLIPSE Simulators: • ECLIPSE 100 = ECLIPSE Black Oil • ECLIPSE 300 = ECLIPSE Compositional • ECLIPSE 500 = ECLIPSE Thermal K.FEKI

112

How to start? To run simulation you need an input file with all data concerning reservoir and process of its exploitation. Input data for ECLIPSE is prepared in free format using a keyword system. Any standard editor may be used to prepare the input file. Alternatively ECLIPSE Office may be used to prepare data interactively through panels, and submit runs. The name of input file has to be in the following format: FILENAME.DATA Input data file An ECLIPSE data input file is split into sections, each of which is introduced by a section-header keyword. A list of all section-header keywords is given in following, together with a brief description of the contents of each section and examples of keywords using in file code. Note that all keywords in input file have to be in proper order The keywords in the input data file (including section-header keywords) are each of up to 8 characters in length and must start in column 1. All characters up to column 8 are significant. Any characters on the same line as a keyword from column 9 onwards will be treated as a comment . K.FEKI

113

ECLIPSE files and file extensions User defined data • General data set: • General data set: • Include:

~ . Data ~ . GRDECL ~ . INC

Error / warnings + Text outputs

• Text file: Results

~ . PRT

• Geometry: • INITIAL state: • 1 D results: • 2 D / 3 D results:

~ . EGRID / ~ . GRID ~ . INIT ~ . SUMMARY ~ . RESTART

Use Windows NOTEPAD and NOT Word to edit files.

K.FEKI

114

ECLIPSE DATA FILE - GENERAL INPUT RULES SECTION KEYWORDS

The input data file for ECLIPSE consists of 8 sections, in the order shown • Each section must begin with the section keyword before specifying any data or keywords for that section. • All section keywords must start in column 1.

K.FEKI

115

ECLIPSE DATA FILE - GENERAL INPUT RULES TABLES • Multiple tables are specified using only one keyword. • Each table is ended with a slash. • ECLIPSE will perform interpolation in a table if a 1* is specified.

116 K.FEKI

ECLIPSE DATA FILE - Format

132 character limit

Comments denoted by --

Any unset items after terminating slash are defaulted

Defaults are taken for the next four items Keywords start in the first column

Comments can be placed after terminating slash

K.FEKI

117

Section header keywords The list of section-header keywords in proper order

RUNSPEC GRID EDIT PROPS REGIONS SOLUTION SUMMARY SCHEDULE

A data record has to be ended with a slash [/] K.FEKI

118

How ECLIPSE Sections Relate to the Equation

• Flow = Transmissibility * Mobility * Potential Difference Geometry and Properties

Fluid Properties

Well Production

GRID

PROPS

SCHEDULE

EDIT

REGIONS

SOLUTION

K.FEKI

119

Section header keywords RUNSPEC Title, problem dimensions, switches, phases present, components etc. GRID The GRID section determines the basic geometry of the simulation grid and various rock properties (porosity, absolute permeability, net-to-gross ratios) in each grid cell. From this information, the program calculates the grid block pore volumes, mid-point depths and inter-block transmissibilities.

EDIT Modifications to calculated pore volumes, grid block centre depths and transmissibilities.

K.FEKI

120

Section header keywords SUMMARY

Specification of data to be written to the Summary file after each time step. Necessary if certain types of graphical output (for example water-cut as a function of time) are to be generated after the run has finished. If this section is omitted no Summary files are created. SCHEDULE Specifies the operations to be simulated (production and injection controls and constraints) and the times at which output reports are required. Vertical flow performance curves and simulator tuning parameters may also be specified in the SCHEDULE section.

K.FEKI

121

RUNSPEC section TITLE DIMENS

title number of blocks in X,Y,Z directions

OIL, WATER, GAS, VAPOIL, DISGAS

FIELD/METRIC/LAB WELLDIMS

unit convention

well and group dimensions

UNIFIN

indicates that input files are unified

UNIFOUT

indicates that output files are unified

START

start date of the simulation

NOSIM

data checking only, with no simulation

NB: ECLIPSE automatically creates the RUNSPEC section for cases built in Petrel.

122 K.FEKI

GRID section

TOPS

DX, DY, DZ

PERMX, PERMY, PERMZ

PORO

Depths of top faces of grid blocks for the current box; data is taken from Structure map, and geological model from IRAP

X,Y,Z-direction grid block sizes for the current box; data is taken from Isopac map, and geological model

X,Y,Z-direction permeabilities for the current box; data is taken from Isopac map, and geological model from IRAP Grid block porosities for the current box; data is taken from Isopac map, and geological model from IRAP

123 K.FEKI

Minimum GRID Section  Required properties for each cell in the model: o Geometry: • Cell dimensions • Cell depths. o Properties: • Porosity • Permeability • Net-to-gross or net thickness.  If net thickness is not included, ECLIPSE assumes it is 1.

K.FEKI

124

Block-Centered vs. Corner Point: Geometry Eclipse Keyword

K.FEKI

125

Define Corner Point Grid

COORD --4 coordinate lines --xtop ytop ztop

xbot ybot zbot

0

0

7000

0

0

7100 -- line 1

500

0

7000

500

0

7100 -- line 2

0

500

7000

0

500

7100 -- line 3

500

500

7000

500

500

7100 -- line 4

/ ZCORN

--depths of 16 corners 7000 7000 7000 7000 -- 4 corners on face A 7050 7050 7050 7050 -- 4 corners on face B 7050 7050 7050 7050 -- 4 corners on face C 7100 7100 7100 7100 -- 4 corners on face D /

K.FEKI

126

Define Corner Point Grid One property per cell (NX * NY * NZ):

 Values must also be defined for inactive cells.  Explicit values only.  ECLIPSE has no facilities for entering data as a function.  Petrel, FloGrid, Office, and FloViz have property calculators: • Define the property with the pre-processor. • Export the property as a text file (*.grdecl). • Use the INCLUDE keyword.  If the case is built in Petrel, drop the property in the Define Simulation Case process. K.FEKI

127

Input Examples (1)

K.FEKI

128

Input Examples (2)

K.FEKI

129

Cell Property Definition Using Petrel

 Properties are assigned to each cell during upscaling and exporting to a file.  The INCLUDE keyword is used to load the properties from Petrel.  If the case is built in Petrel, drop the property in the Define Simulation Case process. INCLUDE BRILLIG_props.GRDECL /

K.FEKI

130

Introducing a Cartesian LGR

CARFIN --Name LGR1 1. 2. 3. 4.

I1 2

I2 4

J1 2

J2 7

K1 1

K2 1

NX NY 6 18

NZ 1

Wells 1 /

Choose global cells to refine. Decide on LGR size. Insert CARFIN. Update LGR in RUNSPEC.

K.FEKI

131

LGR Property Modification  Local cells automatically inherit properties from global host cells.  Can be overridden using most GRID section keywords.  Must be placed after specification keyword (CARFIN) and before ENDFIN or subsequent specification keyword.

CARFIN --Name I1 I2 J1 J2 K1 K2 NX NY NZ Wells LGR1 2 4 2 7 1 1 6 18 1 1 / EQUALS PORO 0.18 / PERMX 150 / / ENDFIN K.FEKI

132

Non-Neighbor Connections (NNCs)

 An NNC allows flow between cells without adjacent IJK indices.

    

Pinchouts and unconformities (PINCH and/or MINPV) Faults Aquifers often require NNCs Local grid refinement (LGRs) User-defined NNCs.

K.FEKI

133

Non-Neighbor Connections (NNCs)

LGR Fault Throw

Global cell (1,2,1) has NNCs to LGR cells (1,1,1), (1,2,1), and (1,3,1). ECLIPSE calculates.

(4,2,1) has NNCs to (3,2,3) and (3,2,4). ECLIPSE calculates in Corner Point grids (default transmissibility NEWTRAN).

Unconformity (12,2,5) has NNC to (12,2,7). PINCH or MINPV must be used. K.FEKI

134

Transmissibility Options in ECLIPSE:NEWTRAN Based on the mutual interface area of the two cells A dip correction is automatically accounted for (using the vector distance from the cell center to the cell face center). Default for corner point grids

K.FEKI

135

Transmissibility Modifications

K.FEKI

136

Transmissibility Modifications

 For a report in the PRT file, use  RPTGRID (requests report of many GRID section keywords, including ALLNNC)  For 3D viewable output, use  Geometric data (*.egrid), GRIDFILE 0 1/  Static properties (*.init), INIT.

K.FEKI

137

EDIT Section

Cell geometry, pore volume, and transmissibility are calculated in the GRID section. These properties are modified in the EDIT section.

EDIT is optional.

K.FEKI

138

EDIT Section

Some GRID section output can be modified in EDIT section: DEPTH, PORV, and TRAN (X, Y, R, THT, Z)

Operators: MULTIPLY, BOX, EQUALS, COPY, MINVALUE, and MAXVALUE

Others: EDITNNC, MULTPV, and MULTFLT MULT (X, Y, R, THT, Z, etc.) are allowed but not recommended.

K.FEKI

139

PROPS Section

 The PROPS section contains pressure-dependent and saturation-dependent properties of the reservoir fluids and rocks.  Fluid information required (for each fluid in RUNSPEC): • Fluid PVT as a function of pressure • Density or gravity

 Rock information required: • Relative permeabilities as a function of saturation • Capillary pressures as a function of saturation • Rock compressibility as a function of pressure. K.FEKI

140

water relative permeability and capillary pressure as functions of Swv

SOF3

oil relative permeability as a function of So in three phase system

SGFN

gas relative permeability and capillary pressure as functions of Sg

PVTO

FVF and viscosity of live oil as functions of pressure and Rs

PVTG

FVF and viscosity of wet gas as functions of pressure and Rv

PVTW

FVF, compressibility and viscosity of water

DENSITY

ROCK

reservoir fluid properties from PVT analysis

SWFN

saturation tables from special core analysis

PROPS section

stock tank fluid densities rock compressibility

K.FEKI

141

Dead Oil Entry Data Using PVDO and PVCDO

K.FEKI

142

Live Oil Data Entry Using PVTO

K.FEKI

143

Wet Gas Data Entry Using PVTG

PVTG --Pg 60 120 180 240 300 360 560 /

Rv 0.00014 0.00012 0.00015 0.00019 0.00029 0.00049 0.00060

Bg 0.05230 0.01320 0.00877 0.00554 0.00417 0.00357 0.00356

Mu 0.0234 0.0252 0.0281 0.0318 0.0355 0.0392 0.0393

/ / / / / / /

K.FEKI

144

Dry Gas Data Entry Using PVDG

PVDG --P 1214 1414 1614 1814 2214 2614 3014

Bg 13.947 7.028 4.657 3.453 2.240 1.638 1.282

Mu 0.0124 0.0125 0.0128 0.0130 0.0139 0.0148 0.0161

/

RVCONST --Rv 0.0047

Pd 1214

/

K.FEKI

145

Reference Densities

K.FEKI

146

EXTRAPMS

 This keyword instructs ECLIPSE to warn you whenever extrapolations are made to PVT (or VFP) tables.  ECLIPSE stores PVT tables internally as the reciprocals of FVF and Viscosity * FVF.  If insufficient PVT data is supplied, ECLIPSE may extrapolate the PVT table data to inaccurate or non-physical values!

K.FEKI

147

Using Multiple PVT Regions

 Necessary keywords: • In RUNSPEC, check TABDIMS and EQLDIMS. • In PROPS, include multiple tables (some may be defaulted). • In REGIONS, include PVTNUM and EQLNUM.

K.FEKI

148

ROCK Keyword

Required because the pore volume varies under pressure Simplest approach: •ROCK keyword •Rock compressibility is reversible and the same everywhere.

K.FEKI

149

Make fluid model using PETREL 1. Process panel. 2. Simulation

3. Make fluid model 4. Define Compositional Reservoir Fluid (Oil, Gas, water) 5. Build Fluid Model from Different Correlations

K.FEKI

150

Purpose of Saturation Functions

K.FEKI

151

Significant Saturation Endpoints 1

K.FEKI

152

Significant Saturation Endpoints 2

K.FEKI

153

Saturation Function Keyword Family 1

K.FEKI

154

Saturation Function Keyword Family 2

K.FEKI

155

Saturation Function using PETREL 1. Process panel. 2. Simulation

3. Make rock physics functions 4. Create relative permeabilities from Corey correlation 5. Create a Rock Compaction Function 6. Create Rock Compressibility

K.FEKI

156

Saturation Function Keyword Family 2

RPTPROPS •Controls output from PROPS section to the PRT file INIT •Saturation functions and PVT data are written to the INIT file. •Can be displayed in 2D and 3D (Petrel, Office, FloViz, FloGrid) FILLEPS

All saturation end points written to the INIT file

K.FEKI

157

REGIONS section FIPNUM

fluid-in-place regions

SATNUM

saturation table regions

EQLNUM

equilibration regions

PVTNUM

PVT data regions

K.FEKI

158

Use: Reporting Purposes

•

FIPNUM (fluid in place regions) are defined in the REGIONS section. In the SOLUTIONS section: RPTSOL FIP=2 / • The PRT file now shows the fluids in place both originally and at each report step.

K.FEKI

159

Output Controls

K.FEKI

160

SOLUTION Section

The objective is to set up: • Initial pressures • Initial saturations The SOLUTION section contains the information needed to initialize the model. ECLIPSE will then define: • Initial pressures and phase saturation in each grid cell • Variation of reservoir fluid properties with depth • Initial ANALYTICAL AQUIFER conditions

K.FEKI

161

SOLUTION section

EQUIL

RESTART

RPTSOL

fluid contact depths and other equilibration parameters; data taken from well testing

name of the restart file

report switches for SOLUTION data

162 K.FEKI

ECLIPSE Initialization Options

Equilibration: ECLIPSE computes initial pressures and saturations using data entered with the EQUIL keyword.

Restart: ECLIPSE reads the initial solution from a restart file created by an earlier run of ECLIPSE.

K.FEKI

163

EQUIL  Sets the contacts and pressures for conventional hydrostatic equilibrium.  EQUIL items are interpreted differently, depending on the phases present.  May have more than one equilibration region (see EQLDIMS).

EQUIL --

D

7000

P

OWC

4000 7150

Pcow

GOC

Pcog

RSVD/PBVD

RVVD/PDVD

0

1*

1*

1*

1*

K.FEKI

N 0

/

164

Block-Centered Equilibrium (1)

K.FEKI

165

Block-Centered Equilibrium (2)

K.FEKI

166

Block-Centered Equilibrium (3)

K.FEKI

167

Matching Initial Water Saturation You often have initial water saturation distribution BUT need EQUIL for pressure, other phase saturations, and more. 1. Input saturation tables as usual, with non-zero Pcow. 2. Enter initial water saturation array using SWATINIT in PROPS section. 3. Enter EQUIL keyword as usual. ECLIPSE scales Pcow to match initial water saturation given in SWATINIT.  Check that scaled Pcow is physically reasonable (INIT file).  PPCWMAX limits maximum capillary pressure scaling. K.FEKI

168

Initial conditions using PETREL

1. 2. 3. 4.

Process panel. Simulation Make fluid model Initial conditions

K.FEKI

169

Restart Runs

(Initialization Run)

Field Production Rate

 The solution at the end of the initialization is set as start conditions for the history match.  Why bother to recalculate initial saturations and pressures?  Restarts save simulation time!

Cell saturations and pressures recorded

(Restart Run)

Time

K.FEKI

170

Aquifer Modeling

 ECLIPSE Blackoil includes these aquifer options:  Numerical aquifer  Analytical aquifer • Carter-Tracy aquifer • Fetkovich aquifer  Flux aquifer  Grid cell aquifer.

K.FEKI

171

Numerical Aquifer Nominate grid cells below the OW contact (AQUNUM). Attach the aquifer to the reservoir using AQUCON. Leave a row of water cells between the aquifer and the oil zone.

K.FEKI

172

Fetkovich Aquifer Fetkovich aquifers are based on a pseudo-steady state productivity index and the material balance between aquifer pressure and cumulative influx. These are best suited for smaller aquifers which may approach psuedo-steady state quickly. In the SOLUTION section: 1. Set up lists of aquifers with AQUALIST. 2. Define the aquifer with AQUFETP. 3. Connect the aquifer with AQUANCON. K.FEKI

173

Carter-Tracy Aquifers Carter-Tracy aquifers use tables of dimensionless time td versus dimensionless pressure Pd(td) to determine the influx. Carter-Tracy approximates a fully transient model. In the SOLUTION section: 1. 2. 3. 4.

Set up lists of aquifers with AQUALIST. Define the aquifer with AQUCT. Define pressure response with AQUTAB. Connect the aquifer with AQUANCON.

K.FEKI

174

Flux Aquifers  The user directly specifies the flux rate:

Qai  Fa Ai mi

Fa = the flux Ai = the area of the connecting cell block mi = an aquifer influx multiplier

 It can be negative, representing flux out of the reservoir. The flux rate can be modified in the SCHEDULE section.  In the SOLUTION section: 1. Set up lists of aquifers with AQUALIST. 2. Specify the aquifer with AQUFLUX. 3. Connect the aquifer with AQUANCON. K.FEKI

175

Grid Cell Aquifer Simulation model extends over the water zone. No extra keywords are necessary.

K.FEKI

176

Aquifer modeling: PETREL Define Aquifer area (polygon) Define Aquifer Type (Numerical, Carter tracy, Fetkovich) Describe Aquifer Properties

K.FEKI

177

SUMMARY section FOPT

Field Oil Production Total

FOPR

Field Oil Production Rate

FGOR

Field Gas-Oil Ratio

FWIR

Field Water Injection Rate

FOE

Field Oil Efficiency

FPR

Field PRessure

WBHP

Well Bottom Hole Pressure

FWCT

Field Water CuT

WOPR

Well Oil Production Rate

178 K.FEKI

SUMMARY section

K.FEKI

179

SCHEDULE section report switches to select which simulation results are to be printed at report times

RPTSCHED TUNING WELSPECS

COMDAT

time step and convergence controls introduces a new well, defining its name, the position of the wellhead, its bottom hole reference depth and other specification data specifies the position and properties of one or more well completions; this must be entered after the WELSPECS

WCONPROD

control data for production wells

WCONINJE

control data for injection wells

WCONHIST

observed rates for history matching wells

TSTEP or DATE

advances simulator to new report time(s) or specified report date(s) 180 K.FEKI

SCHEDULE section  The SCHEDULE section is used to specify: • Well operations to be simulated • Times (TSTEP and DATES) to be simulated • Simulator tuning parameters.  The SCHEDULE section often is used in two modes: • History matching: Specify actual wells, facilities, and production/injection. • Prediction: Specify control mechanisms, new wells, and

economic limits.

K.FEKI

181

History Matching vs. Prediction

K.FEKI

182

History Matching vs. Prediction

1. Specify output. 2. Specify wells, VFP tables, completions, and rates. 3. Advance the simulation: • Specify old well rates. • Specify any workovers. • Specify any new wells. 4. Repeat.(Step 3) 5. End of history match.

K.FEKI

183

VFP Curve Specification The VFP table is a table of BHP versus FLO, THP, WFR, GFR, and ALQ. FLO is the oil, liquid, or gas production rate. WFR is the water-oil ratio, water cut, or water-gas ratio. GFR is the gas-oil ratio, gas-liquid ratio, or oil-gas ratio. ALQ is a variable that can be used to incorporate an additional parameter, such as the level of artificial lift. Petrel can be used to create and analyze VFP tables using the PIPESIM engine and the VFP manager. VFPi is the ECLIPSE family preprocessor that can be used to generate this keyword. K.FEKI

184

VFP Table Usage

K.FEKI

185

Well Specification: WELSPECS

 Introduces new well and specifies some of its general data.  Compulsory keyword: A well must be introduced with this keyword before it can be referenced in any other keyword.

WELSPECS --nm grp I J refD phase P1 G 2 2 1* OIL P21 G 8 1 1* OIL I20 G 20 1 1* WAT /

drad -1 / -1 / -1 /

K.FEKI

186

Well Specification: WELSPECS

Pw

ECLIPSE Model

 A significant part of history matching is adjusting well parameters to achieve the correct inflow performance.

rd Physical Model

 Productivity index (PI) and well drawdown depend upon grid block size in ECLIPSE.

K.FEKI

P* average reservoir pressure

Pw, well BHP rd, re drainage radii

re Pc, cell pressur e

187

Measure of Pressure

 Appropriate drawdown behavior is achieved by adjusting the productivity index. • Request WBP and WBP9 in the SUMMARY section. • Use the approximation: WBP 9  WBHP  H WPIMULT  WBP  WBHP  H

WBP 9

WBP 9 WBP

Where: WBHP = bottomhole pressure from well test

H = hydrostatic correction (midperfs to ECLIPSE datum)

K.FEKI

WBP 9

WBP 9

188

Completion Specification: COMPDAT

 Specifies the position and properties of one or more well completions. COMPDAT --nm I P1

J Ku

Kl status sat CF S

Dwell Kh

2* 1 10 OPEN

1*

1* 0.583

/

P21 2* 1 10 SHUT

1*

1* 0.583

/

I20 2* 1

1*

1* 0.583

/

5 AUTO /

K.FEKI

189

Historical Flow Rate: WCONHIST

 Used to set a history-matching well’s observed flow rate.  Control modes: ORAT, WRAT, GRAT, LRAT, and RESV  WCONINJH is the injection counterpart.

DATES 1 'FEB' 1970 / / WCONHIST --nm stat ctl-by P1

OPEN

ORAT

oil

wat

822.3

0.58

gas

VFPtbl

6122.5

5* /

/

Repeated for each date K.FEKI

190

Simulation Advance and Termination

• • •

DATES 1 JAN 1 JUN

• •

TSTEP 1 /

Advance to 12.00 am on 2/6/2012

• •

TSTEP 0.2 /

Advance by 0.2 days

•

END

2012 2012

/ /

Advance to 12.00 am on 1/1/2012 Advance to 12.00 am on 1/6/2012

-- Conclude simulation

K.FEKI

191

Common Workover Keywords

 WELOPEN • Open and shut wells at a known time  COMPDAT • Alter completion properties to simulate plugs, squeezes, and frac jobs  WELPI and WPIMULT • Modify well PI

K.FEKI

192

History Strategy in Petrel

 Import • Well paths (deviation surveys) • Well completion data o Completion intervals o Workover events o Production/injection data.  Create history strategy.  Export case: • ECLIPSE SCHEDULE section keywords

K.FEKI

193

Predictions

K.FEKI

194

Predictions

1. 2. 3. 4.

Specify/change output frequency. Specify wells, VFP tables, and completions. Specify groups. Specify group and well: • Economic limits and well tests Choose keywords that will cause ECLIPSE to treat • Automatic workovers, drilling, etc. wells according to the 5. Advance the simulation. company operating the field. 6. End of prediction.

K.FEKI

195

Production Forecasts

K.FEKI

196

Well Controls

K.FEKI

197

Well Controls: ECLIPSE keywords

K.FEKI

198

Primary and Secondary Well Controls Primary controls

•Target rate of a principal phase; or •Fixed pressure(either bottom-hole or tubing-head) Secondary constraints •maximum rates of one or more phases •maximum ratios (GOR, WCT, WGR) •limiting pressures •limiting ΔP Eclipse will operate the well under the primary control unless one of the secondary constraints is violated Controls may be re-set at any time during the simulation

K.FEKI

199

Production Well Controls –Example 1

K.FEKI

200

Production Well Controls –Example 2

K.FEKI

201

Production Well Controls –Example 3

K.FEKI

202

Production Well Controls –Example 4

WCONPROD --nm status ctl-by Oil

P1 OPEN

W-G-Limit BHP THP VFP#

ORAT 4000 2000 3* 3000 2* /

 P1 is under oil rate control.  P1 is moved to BHP control.

Water cut is rising and BHP is dropping.

The waterflood has reached P1 but is not providing enough pressure support.

BHP rises due to pressure support from the aquifer and injector.

 P1 is switched to control by water rate.

K.FEKI

203

Other Well Control Keywords -WELTARG

K.FEKI

204

Group Production Control  Group control is used to mimic field operation.  Examples: • Platform A has a certain water-handling capacity (GCONPROD). • Facility B uses 25% of its gas production to run a treater and sells the remaining gas (GCONSUMP). • A voidage replacement scheme is implemented in Block C (GCONINJE). • To maintain pipeline capacity, Company D drills wells whenever the field production falls below a rate (PRIORITY).

K.FEKI

205

RESTART

 The solution at the end of the history period is set as start conditions for the prediction runs.

Field Production Rate

Cell Saturations and Pressures Recorded

 Why bother to recalculate past saturations and pressures?  Restarts save simulation time!

History Period

(Base Run)

Prediction Period

(Restart Run)

Time

K.FEKI

206

Convergence problems

– Data errors: • Special characters and missing values. – Grid geometry: • Small PV cells next to large PV cells. – LGRs: • LGR smaller than drainage radius. • Initial contacts outside LGR. – Dual porosity: High value of sigma. K.FEKI

Plot and Fix!

Inactivate with PINCH or MINPV! 207

Report

K.FEKI

208

Petrel Interface

K.FEKI

209

Explorer Panes

Contain all Fault models and 3D grids

Contains all imported data and all subjects that are not a part of the 3D grid

Bold item Click on an object name to activate it

K.FEKI

210

Explorer Panes

Anew case is added each time a simulation or volume case is defined

Used to select lines to show in the function window. Used to display 3D properties in 3D window.

K.FEKI

Only one process can be active at the time

211

Display Tools

target zoom

Move

View all displayed data

View from specific position

K.FEKI

Select/Pick mode- allows for selecting objects and getting information bout them in the status bar

212

ECLIPSE/PETREL WORKSHOP Field SNARK is at its primary recovery stage. The geological information indicates that there are 12 reservoirs layers. Seismic data indicates that there is an aquifer attached to the field, probably from southern direction. In order to estimate future production from the field, a simulation study will be conducted using ECLIPSE. The first stage of the process is to construct a base case simulation model which will be later calibrated to past production measurement by history matching. Model dimension Based on the amount of data available and the computer resources, its has been decided to carry out the simulation using a 3D model comprising 12 simulation layers, corresponding to the 12 geological layers, and 24 columns of cells in the lateral direction and 25 rows of cells

in the tranverse direction(ie. 24X25X12). The aquifer volume will be modeled by an analytical aquifer(Fetkovich). There are 5 producers. Producers that are close to the aquifer may be converted to injectors later. Up to two infill wells may be drilled at a later date. K.FEKI

213

ECLIPSE/PETREL WORKSHOP Fluid Properties The reservoir oil is initially undersatured. But with production, the reservoir pressure has

dropped below the bubble point pressure. The fluid properties are believed to be constant throughout the reservoir. 1.Create the RUNSPEC section appropriate for the simulation model described above. (Hint: Make sure to insert all the necessary dimensioning keywords such as WELLDIMS). 2. Request unified input and output and field units. 3.Choose START date for this simulation of 1st January 1998. 4.Ensure the data file is named SNARK.DATA. Save it in a convenient location in a sub diretory of your home directory K.FEKI

214

ECLIPSE/PETREL WORKSHOP Layer

Kx, Ky (md)

poro

1

231

0.17

2

244

0.17

The Kz/Kx ratio of all layers is 0.1

3

29

0.06

A corner-point geometric representation of the reservoir

4

250

0.17

has been exported from petrel –SNARK.GRDECL

5

257

0.17

6. update the PROPS section by PVT and saturations

6

191

0.17

7

333

0.19

8

334

0.19

9

291

0.18

10

335

0.18

11

287

0.18

12

262

0.17

5.The data in the table above has been obtained from wells drilled throughout the reservoir.

tables, the water formation volume factor Bw is 1.013 rb/stb at 3118 psia with constant water viscosity 0.4cp and compressibility 2.7x10-6 (psi)-1. the rock compressibility is 2.8x10-6 (psi)-1 @ 5801.5 psia, the relative density of oil, water and gaz are 42.28 lb/ft3 , 62.43 lb/ft3 and 0.0971 lb/ft3.

Kz/Kx=0.1 throughout reservoir

K.FEKI

215

ECLIPSE/PETREL WORKSHOP 7. From special core analysis the following two phase relative permeability and

capillary pressure curves have been obtained. Sw

S0

Krw

kro

Pcow

Sg

S0

Krg

kro

Pcog

0.20

0.8

0.00

0.9

50

0.00

0.8

0.000

0.900

0

0.22

0.78

0.000

0.803

45

0.06

0.74

0.000

0.525

0

0.3

0.7

0.001

0.487

25

0.10

0.7

0.000

0.375

0

0.4

0.6

0.009

0.221

12.5

0.14

0.66

0.000

0.213

0

0.5

0.5

0.045

0.078

6.3

0.19

0.61

0.002

0.106

0

0.6

0.4

0.154

0.014

2.5

0.24

0.56

0.006

0.042

0

0.7

0.3

0.387

0.001

1.3

0.29

0.51

0.013

0.011

0

0.73

0.27

0.480

0.000

1.1

0.33

0.47

0.035

0.001

0

0.8

0.2

0.800

0.000

0.8

0.37

0.43

0.061

0.000

0

1

00

1

0.000

0

0.80

0.00

0.900

0.000

Oil-water relative permeability and Capillary Pressure

Oil-Gas relative permeability and Capillary Pressure

K.FEKI

216

ECLIPSE/PETREL WORKSHOP 8-Create REGIONS section of SNARK.DATA. Remember to update the RUNSPEC section as necessary 9. Include file FIPNUM.GRDECL, which has four fluid-in place (FIP) regions, one for each fault block, using the FIPNUM keyword. The property may be created and exported from Petrel. 10. Create additional flui-in-place regions, one for each layer, named FIPLAYER

10. Run SNARK.DATA. Verify that the saturation functions and PVT data are correct.

PVT analysis indicates that only one oil type exists throughout the reservoir. It had a bubble point of 1062.2 psia, and has a solution GOR of 0.973 scf/stb. From the results of wells drilled throughout the reservoir the OWC has been determined as 8200 ft. This is coincident with the free water level. From well logs, the pressure is 3035.7 psia at depth of 7000ft. K.FEKI

217

ECLIPSE/PETREL WORKSHOP The geologist believes that an aquifer is attached to the reservoir on the southern side of the central fault block. It is stimated to contain approximately 1X10^7 stb of water and could supply the reservoir at a rate of 5 bbl/day/psi. A fetkovich aquifer model should be

used. Place its datum depth at the OWC and ensure it is in initial equilibrium with the reservoir. Total compressibility is around 1X10^-5 1/psi, PI is 5 stb/day/psi.

10. Create the appropriate SOLUTION section for SNARK.DATA using the above information. Use center Block equilibration (EQUIL item9=0).

11. Request output of an initial restart file at time zero. Request output of Fluid-in-place

reports for the field, fault blocks and layers to the PRT file. 12.Review the summary vectors in SUMMARY section of SNARK.DATA.

K.FEKI

218

ECLIPSE/PETREL WORKSHOP 13.Advance the simulation vectors by several months(or years) by inserting the following into the SCHEDULE section. This will allow you to check the stability of the simulation.

RPTSCHED ‘FIP’=3’ ‘ RESTART=2’ / TSTEP 10*30 / END 14. Run SNARK.DATA, ensure that NOSIM is commented out if it is present in your data file. Is the model stable? Find the OIIP (total), OIIP FIPNUM=1, OIIP FIPLAYER=10

Five vertical oil producers have been drilled in the reservoir. Four are located in the central fault block and one in western block. They are named PROD1, PROD2, PROD3, PROD4 and PRODUCER, respectively. All wells have an internal diameter of 0.625 feet and a skin factor of 7.5. Their well head location and perforation intervals in I, J and K format are: K.FEKI

219

ECLIPSE/PETREL WORKSHOP Well Name

Group

Well Head

Perforation

I

J

k1

K2

PROD1

Center

13

8

1

12

PROD2

center

7

20

1

10

PROD3

center

16

16

2

9

PROD4

Center

17

21

1

2

PRODUCER

West

6

8

1

10

All wells were measured with production rates and bottom hole pressure every three months. The history keywords were prepared with shedule or Petrel and exported in File HIST.SCH file. The history match phase is complete on 1st January 2008. For the history matching exercise, new grid properties are available in the file GRID_PROPS.INC, which has varying permeability and porosity values in each layer. The geologist suspects that the fault between the well Producer and the others is not fully open.

K.FEKI

220

ECLIPSE/PETREL WORKSHOP 15.Copy SNARK.DATA to SNARK_HIST.DATA 16.Reolace the Grid properties (PERMX, PORO, ect) with the INCLUDE file GRID_PROPS.INC and INCLUDE FAULTS.INC

17.Remove the Keywords from the SCHEDULE section that we added during the previous exercise. To history match our models, we must compare actual well production and pressure to simulation results. Well information, including locations, completions and rates are gathered and entered into the SCHEDULE section. 18. Create keywords for well location and completions from scratch for SNARK_HIST.DATA 19. Include well production history file HIST.SCH.

20.Request restart file output at every reporting step. Request also output of fluid in-place reports, CPU usage and a summary of the convergence of the Newton iteration.

K.FEKI

221

ECLIPSE/PETREL WORKSHOP 21. To compare the simulation results with observed data you need to request output of the production rate history for oil, water and gas as well as bottom-hole pressure(BHP) for all wells to the summary file.

22.Run SNARK_HIST. DATA, this becomes our base case for history matching. Use SNARK_HIST.GRF to analyze the results in ECLIPSE office. Use the Jump the well icon (OR view>Jump to well/Group) to look at the results of each well.

23.The geologist suspects that FAULT1 is not fully open to fluid flow. You need to do a sensitivity analysis on the fault’s transmissibility. *Copy the base case,

SNARK_HIST.DATA, to SNARK_FTM05.

K.FEKI

222

ECLIPSE/PETREL WORKSHOP *Define the faults using the provided INCLUDE file, FAULTS.INC. Use a fault transmissibility multiplier of 0.5 for fault1. Run this case. Build another sensitivity run in a similar manner SNARK_FTM0. 24.You can use FTM_SENSITIVITY.GRF to help analyse the differences between the three cases. 25. There is also a high amount of uncertainty assiciated with the size and deliverability of the aquifer. Your next task is to perform sensitivity

analysis on the aquifer volume and its productivity index. *Copy the base case, SNARK_HIST.DATA, to SNARK_AQV9.DATA *Change the value of the aquifer’s initial volume to 1x10^9 stb, run the case. *Built a set of sensitivity runs in a similar fashion. Consider the following cases: SNARK_AQV11-aquifeVolume =1x10^11 stb SNARK_AQPI50-Aquifer Productivity index=50 stb/day/psi SNARK_AQPI500-Aquifer Productivity index=500 stb/day/psi K.FEKI

223

ECLIPSE/PETREL WORKSHOP *Use AQ_SENSITIVITY.GRF to analyse the results of the fault transmissibility, aquifer volume and aquifer productivity index sensitivity studies. Fill in the table below with your Observation. Fault Transmissibility Multiplier

Improves/Worsens

1 0.5 0

Aquifer initial volume (stb)

Improves/Worsens

1 x 10^7 1 x 10^9

1 x 10^11 Aquifer PI

Improves/Worsens

5 10

500

K.FEKI

224

Thank You!

K.FEKI

225