Cementing Lab. Nl 09 Sep 99 -a

Cement Lab Introduction Module CF116 09 Sep 99

Laboratory Functions

Two types of Laboratory testing : 1. Performance Evaluation  Slurry Design Stage 

Measurement of specific slurry properties under simulated downhole conditions.

 Execution Stage 

Monitor preparation of blended materials

2. Chemical Characterisation  Quantitative or qualitative analysis of the slurry

components prior to mixing. Cement  Additives  Mix Fluid 

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Performance EvaluationSlurries  Governed by the API committee on “Standardisation of Oilwell Cements” (10A & 10B)

 Publication consists of;  

Test specifications for neat cement slurries Operational testing procedures for all slurries

 Procedures designed to simulate

downhole conditions

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

Pressure



Temperature

Performance EvaluationSpacers/Washes

 Evaluation of the cleaning effect

 Compatibility with Cement  Thickening Time Excerpt API Spec 10B  Fluid Loss  Compressive Strength  Rheology  Effects on mud 

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Rheology

Fluid Compatibility  API Spec. 10 contains the procedures for

measuring the compatibility of fluids.

 The effects of a spacer or chemical wash

are investigated.

 Compatible fluids result in very equal sets

of Fann 35 readings.  Large difference between test results

indicates incompatibility. 5

Chemical Characterization Four types of samples are examined  Cement Powder  C3A, C3S, C2S, C4AF and Gypsum

 Dry Blended Cement  Consistency

 Set Cement  Mix water

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Sample Preparation

Sampling  Sample acquisition  Prior to shipment (batch number)  From rig site  ALWAYS use actual field samples & labelled.  Sampling procedures as per API spec 10B

Section 4   

Cement & blends at field location Dry & liquid cement additives at field location Mixing water

 Disposal  Comply with all regulatory requirements

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Slurry Design

Slurry Properties  Free Water & Slurry Sedimentation Water separation from static slurry Migrates upward, accumulates in pockets

or at top of cement column.

Results in incomplete zonal isolation

 Density Balance sub-surface pressures Cement final strength

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Slurry Properties - cont.  Pumpability (Slurry Consistency)  Length of time slurry remains in a pumpable

fluid state (Job Time + 1 Hour)  Fluid Loss  Slurry dehydration during placement phase

 Rheology  Slurry flow modelling

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Set Cement Properties  Bonding Cement - Casing & Cement - Formation

 Sulfate Resistance Reaction to magnesium and sodium sulfates; 

Loss of compressive strength



Stress cracking

 Strength Retrogression Cement Shrinkage occurs at >230°F (110°C).

 Permeability Lightweight slurries

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Testing Process LAB ANALYSIS REQUEST(LAR) SLURRY DENSITY

RHEOLOGY

FREE WATER TEST

FLUID LOSS TEST

CEMENT - SPACER - MUD COMPATABILITY

THICKENING TIME TEST

COMPRESSIVE STRENGTH TEST

LABORATORY REPORT

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Laboratory Procedures & Equipment

Lab Analysis Request (LAR)

 Submit LAR to lab requesting a slurry

formulation  Designate additives available for slurry design  Request specific performance parameters;      

Density Rheology ( PV, YP & Gel Strength) Fluid Loss Thickening Time Free Water Compressive Strength

 Provide information on well parameters  Job Type, Depth (MD/TVD)  Temperatures (BHST/BHCT/maxHCT)  Pressure Profiles.

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Laboratory Analysis Report  At the conclusion of Cement Slurry

formulation and subsequent testing a report is produced outlining the following;  Part 1   

Information requested Summary of results Conclusions and recommendations

 Part 2  Laboratory Tests and Results  Part 3  Appendices as necessary

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Slurry Properties

LAR Number Well Conditions

Slurry Formulation

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Typical LAR format generated by LabDB* software

Sample Calculation  Sample volume for slurry testing is 600 ml  Consider the following slurry composed of;  Class G Neat & 44% water Material Class G Cement

Weight (lbs) 94

Absolute Volume (gal) 0.0382

Volume (gal) 3.59

Weight (gram) 42637.7

Volume (ml) 13589.6

Water 44%

41.36

0.1202

4.97

18760.6

18813.5

TOTAL

135.36

8.56

61398.3

32403.1

Calculate for 600 ml : • ratio = Total Volume / 600 ml = 54:1

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Slurry Preparation -

API spec 10B

Section 5  Mixed with a high shear mixer (Waring Blender)  Water and Liquid Additives mixed first.  D20 and polymer need to pre-hydrate prior to

adding dispersant and retarder.

 Add Cement /Solids & mix at 4000 rpm for 15

sec.

 Continue mix at 12,000 rpm for 35 sec.  Mixing procedure not suitable for; Microspheres (D124) Foam slurries

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Slurry Tests - Density & FW  Density Measurement (API Spec 10B Section 6)  Pressurized or Atmospheric Balance  Units are ppg, Kg/m3, SG

 Free Water Test (API Spec 10 Section 6)  Slurry placed in 250ml graduated glass test

tube  Free water (ml) measured after 2 hours

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Static Fluid Loss -

API Spec 10B

Section 10  Simulates amount of fluid loss under pressure against a permeable formation  Use HPHT cell (simulates downhole conditions) 

P = 1000psi, 93°F>T > 194°F (90°C)

 Formation simulated by 325 mesh screen 

Backed up by a 60 mesh screen

 Conditioning procedures as per Section 10.6 &

10.7  Testing procedure as per Section 10.11

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Filtrate Loss  For slurries that dehydrate in less than 30

minutes, Fluid Loss value is obtained by :  The Relationship

F 30= 2Qt 

5.477 t

F30 = Calculated API Filtrate at 30 minu Qt = Vol (ml) of Filtrate at time t (min) t = Time in minutes

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Rheology -

API Spec 10B Section 12

 Correlation between shear stress and

shear rate  Tested with Viscometer (FANN 35) Rotational speed (Shear rate)     

300 RPM 200 RPM 100 RPM 60 RPM 30 RPM

 600 RPM not used. 24

Rheology  6 RPM and 3 RPM readings omitted.  3 RPM reading is used to determine

the fluid gel strength at;  10 seconds & 10 minutes

Rotational Sleeve

Slurry Cup

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BOB (Stationary)

Slurry Tests - cont. Thickening Time

Determine length of time a slurry remains fluid  Pressurized consistometer simulates both;  Temperature  Pressure  Reported in Beardon units of consistency (BC)  Upper fluid limit (API) 100 BC  API spec 10 for P-T schedules (example Fig B-7 in Well Cementing)  Casing,

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Liners, Squeeze cementing

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Thickening Time Test Curve Temperature

Time (min)

0 140 130 120 110 100 90 80 70 60 50 40 30 20 10 0

100 200 deg.F

400

500

Bc

Temp.

Bc

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300

50

100

API Schedules -

API Spec 10B

Section 9.5  Pressure and Temperature  schedules derived from field data  schedules available for casing, liner and squeeze jobs  P-T effect on Thickening Time  continuous exposure to varying P-T profiles  max P-T not necessarily at same point  TOC will be exposed to max P-T while circulating  New Instrumentation & Refine Procedures  API schedules do not cover all factors  dynamic wellbore simulation tool

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Solution - CemCADE

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BHCT Prediction degF ( * 100) 0.5

1.5

3.5

2.5

Formation Annulus Casing Fluids

Max HCT BHCT

Mud Temp. Profile At 180 min

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Slurry Tests - Compressive Strength  Set cement strength under downhole

conditions  Apparatus; Curing Bath (ATM pressure & 82 oC) Curing Chamber (3000 psi & 193 oC)  Procedure.  Measurement Unit  Other methods

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Test Category Sampling Slurry Preparation

Summary of Test Procedures

Slurry Conditioning Thickening Time Static Fluid Loss Compressive Strength Free Water Permeability Rheology Static Gel Strength Expansion Spacer/Wash/Cement Compatibility Particle Analysis (Portland Cement) Chemical Analysis of Dry Blends Chemical Analysis of Mix water

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Equipment Diverter Flow Sampler 2-Speed Propeller Mixer

Atmospheric Consistometer Atmospheric and Pressurized Consistometer HTHP Fluid Loss Cell Water/cooling Bath, Curing Chamber, Hydraulic Press, UCA 250ml graduated glass cylinder Permeameter Rotational viscometer Rotational viscometer Bar mould, Cylindrical sleeves Rotational viscometer, Fluid loss cell, Consistometer, Hydraulic press Blaine permeameter

Procedure Reference ASTM C702, API Spec 10(3) & 10B(4) API Spec 10(5) & 10B(5) See relevant sections for Free water, Fluid loss and Rheology in API Spec 10 & 10B API Spec 10(8) & 10B(9) API Spec 10(App F) & 10B(10) API Spec 10(7) & 10B(7 and 8) API Spec 10(6 and App M) & 10B(15) API Spec 10(App G) & 10B(11) API Spec 10(App H) & 10B(12) API RP 13B(2) & 10B(12.7) ASTM C151

API Spec 10(App P) & 10B(16) ASTM C204

UV absorption spectrophotometry ASTM C114 Wet chemical method API RP 45