2- Criteria For Successful Cementing Jun-00-a

CRITERIA FOR SUCCESSFUL CEMENTING

CRITERIA FOR SUCCESSFUL CEMENTING  Dowell Concept  Job Objective  Mud Removal  Temperature Prediction  Slurry Properties  Special Cement Systems  CemCADE Design  Job Execution  Job Evaluation

2 Initials

Dowell Concept Design - Execute - Evaluate Job Planning & Slurry Design

Logs Well/Job Data Well Post-Job History

3 Initials

Blending Slurry Mixing & Placement

Job Objective

Complete cement sheath w/no mud

•

Isolation of productive zones.

•

Protection of water zones

•

Isolation of problem interval

•

Protection of casing

•

Casing support

or gas channel

Cement bonded bonded to to Cement formations formations Cement bonded to casing Oil or Gas pay Zone

4 Initials

Practices Affecting Primary Cementing

Poor Centralization

Channeling: Incompatible preflush or

Wash out:

incomplete mud

Incorrect flow

removal

regime

5 Initials

Slurry Design Factors Affecting Primary Cementing High Free Shrinkage

water

or Microannllus

Gas Intake

Gas Intake

Water Intake

6 Initials

Mud Removal

 Well Preparation  Mud removal effeciency during the

cementing operation

7 Initials

Mud Conditioning  Lower Density – by removing cuttings and sand

 Reduce Viscosity  Reduce Gel Strength by: – Circulation – Addition of Dispersants – Pipe Movement

 Stabilize Well 8 Initials

Casing Centralizers Centralizer

9 Initials

Casing Centralization R2 R1

Wn

% Stand-off = Wn x 100/ (R1-R2)

10 Initials

Influence of Standoff on Mud Removal 100 % Stand-off ( Centered )

Velocity in Wn / Avg. Velocity

1.O

75 % O.8 50 % O.6 33 1/3 %

O.4

O.2

3

8

10

15

Rate of Flow ( bpm )

11 Initials

20

40

60

80

Effects Of Standoff on Mud Displacement

Mud

Cement

Decreasing Stand-off 12 Initials

Casing Movement

Casing Stationary

ROTATION Gelled Mud

Rotation Started Flowing Cement

Re s po istin si ti v g d ra e m gf ud or d i ce sp c l a an ci b ng ec fo om rc e e

13 Initials

Mud almost removed

Casing Movement RECIPROCATION

Stand-off = 100 %

Mud Stand-off == 20 20 % % Stand-off Cement Slurry

14 Initials

Stand-off = 20 %

Cement - Mud Contamination  Acceleration or Retardation  Reduction of Compressive Strength  Reduction of Hydraulic Bond  Increase of filtrate loss  Change of Rheological Properties 16 Initials

Displacing

Wiper Plugs  Prevent

Mud

Top Plug

– Contamination of Spacer – Contamination of Cement slurry Cement

 Wipe Casing clean  Indicate end of Displacement Bottom Plug

19 Initials

Chemical Washes  Low Viscosity Fluids  Usually Water Based  Contain Surfactants and mud thinners

23 Initials

Chemical Washes What They Do / How They Work

 Separate Mud and Cement – No incompatibility effect

 Remove mud from annulus – Turbulence at low pump rate – Erode, dilute and disperse particles

 Leave casing and formation water wet – Function of the Surfactant

 Provide less hydrostatic pressure – Water or oil-based

24 Initials

Spacers Definition

 Densified viscous fluid separating

mud and slurry Function

 Thorough removal of mud Properties

 Compatible with mud and cements – Mixtures less viscous than thicker fluid – No gel

 Specified rheology – Low for Turbulent Flow – Adjustable for Effective Laminar Flow

26 Initials

How Spacers Work  Turbulent Flow: – – – –

Erosion Dilution Flow all around the pipe Contact Time

 Effective Laminar Flow – Density Hierarchy – Friction Pressure Hierarchy – Flow all around the pipe - Minimum Pressure Gradient – Differential Velocity criterion 28 Initials

Spacers  Water Based Mud – MUDPUSH XT - Turbulent ( fresh ) – MUDPUSH XS - Turbulent ( salt ) – MUDPUSH XL - Effective Laminar ( fresh or salt ) – MUDPUSH WHT - HT Effective Laminar ( fresh or salt )

 Oil Based Mud – MUDPUSH XTO - Turbulent ( fresh ) – MUDPUSH XSO - Turbulent ( salt ) – MUDPUSH XLO - Effective Laminar ( fresh or salt ) – MUDPUSH XEO - HT Turbulent ( oil/water emulsion )

29 Initials

Cement Slurry Properties  Conventional Cement system: – Cement Slurry density – Cement Slurry Rheology – Free water – Thickening Time – Compressive Strength – Fluid Loss Control

 Special Cement System: – GASBLOK Technique – SALTBOND – Others

30 Initials

Cement Slurry Rheology  Friction Pressure  Flow Regime Laminar ( sliding motion - zero flow on walls )

Turburlent ( swirling motion )

32 Initials

Effects of Free Water  Channelling  Incomplete Fill-up

33 Initials

Temperature Prediction  Two Basic influences on downhole

performance of cement – Temperature – Pressure

 Temperature has the biggest influence

and affects – – – – – –

35 Initials

Thickening time Transition time Compressive Strength Fluid loss Rheology Free water

Downhole Circulated Temperature Probe  Where to run: – Wiper Trip – Casing circulation

 How to load: – Drop into DP – Load in treating iron – Launching loop

 Recovery: – In basket over shakers – Usually a maximum of 50% recovered

36 Initials

Maximum Circulating Temperature and Depth Circulation

Cementing

WOC

Maximum Temperature Depth of Maximum Temperature

API BHCT ( 237 F )

Time ( hr:min ), Sub-Units: Open Hole

 CemCADE also predicts – Temperature vs time at a given depth – Temperature of a fluid element ( e.g. 1st sack ) during and after placement – Temperature vs depth at a given time

37 Initials

Fluid Loss control Fluid Loss mL / 30 min Cement Class

D60 %

S1 %

98 F

136 F

98 F

136 F

A

0 0.8 0.8

0 0 2

1000+ 100 300

1000+ 350 -

1:35 3:10 2:20

1:00 2:00 1:40

1.0 1.0 1.3

0 2 0

75 150 35

130 50

4:00+ 3:00 6:00+

3:00 2:05 4:00

1.3

2

50

75

4:00

3:00

0 1.0 1.0

0 0 2

1000+ 150 215

1000+ 100 250

3:20 5:00 1:35

2:00 3:00 1:05

1.3 1.3

0 2

100 125

150 170

5:00+ 1:40

4:10 0:55

G

38 Initials

Thickening Time ( hr: min )

Why use Fluid Loss Control  Maintain constant water-to-solid ratio – Constant Density – Desired Yield – Thickening Time – Compressive strength – Rheology – Constant Properties

 Avoid annular bridging or excessive

pump pressure  Reduce formation damage 41 Initials

CemCADE Job Design  Better zonal isolation

– Optimum mud Romoval Flow Regime  Pump rate  Mud removal effeciency vs stand-off 

– Slurry design

 Well security and control – – – –

No loss circulation No fluid influx No casing collapse Anticipated surface pressure

 Job evaluation – PRISM – CBL Adviser

43 Initials

Job Execution IS EXECUTION AS DESIGNED Real Time Job Monitoring PRISM 44 Initials

On-site Data Acquisition  PRISM – – – –

Pressure, Density, Flow rate sensors Portable acquisition computer Standard remote display Colour ink-jet printer

 Quality of treatment execution through: – Permanent graphical record of treatment in real time – Accurate, reliable data acquisition regardless of environmental conditions – Immediate post-job treatment reports

 Treatment Effeciency through: – Post-job analysis of data which  

45 Initials

(1) ensures pressures and rates were as designed and (2) helps to improve future designs

Post Job Evaluation  Job Design (CemCADE) vs Job Execution

(PRISM)  CBL Adviser  Cement Bond and Variable Density Logs (CBL-

VDL)  Cement Evaluation Log  Dry Test with DST Tools  Pressure Test ( Shoe Bond Test )

47 Initials

Summary Define Cementing Objectives Use Computer Aided Design Improve Mud Displacement – – – – –

Condition mud prior to cementing Use centralizers Rotate and / or Reciprocate Avoid adverse mud cement reations Control displacement rate and sapcer and slurry rheology

 Optimize cement slurry design  Execute Job as per Design  Perform full Post-job Evaluation

48 Initials