Introduction to the Cementing lab

Module CMT 01622-Jun-00

Laboratory FunctionsTwo types of Laboratory testing :1. Performance EvaluationSlurry Design StageMeasurement of specific slurry properties under simulated downhole conditions.Execution StageMonitor preparation of blended materials2. Chemical CharacterisationQuantitative or qualitative analysis of the slurry components prior to mixing.CementAdditivesMix Fluid

Performance Evaluation- SlurriesGoverned by the API committee on Standardisation of Oilwell Cements (10A & 10B)Publication consists of;Test specifications for neat cement slurriesOperational testing procedures for all slurriesProcedures designed to simulate downhole conditionsPressureTemperature

Performance Evaluation-Spacers/WashesEvaluation of the cleaning effect

Compatibility with CementThickening TimeFluid LossCompressive StrengthRheology

Effects on mudRheologyAPI Spec 10B

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.

Chemical CharacterizationFour types of samples are examinedCement PowderC3A, C3S, C2S, C4AF and GypsumDry Blended CementConsistencySet CementMix water

Sample Preparation

SamplingSample acquisitionPrior to shipment (batch number)From rig siteALWAYS use actual field samples & labelled.Sampling procedures as per API spec 10B Section 4Cement & blends at field locationDry & liquid cement additives at field locationMixing waterDisposalComply with all regulatory requirements

Slurry Design

Slurry PropertiesFree Water & Slurry SedimentationWater separation from static slurryMigrates upward, accumulates in pockets or at top of cement column.Results in incomplete zonal isolationDensityBalance sub-surface pressuresCement final strength

Slurry Properties - cont.Pumpability (Slurry Consistency)Length of time slurry remains in a pumpable fluid state (Job Time + 1 Hour)Fluid LossSlurry dehydration during placement phaseRheologySlurry flow modelling

Set Cement PropertiesBondingCement - Casing & Cement - FormationSulfate ResistanceReaction to magnesium and sodium sulfatesLoss of compressive strengthStress crackingStrength RetrogressionCement Shrinkage occurs at >230F (110C). PermeabilityLightweight slurries

Testing ProcessCEMENT - SPACER - MUDCOMPATABILITYTHICKENING TIMETESTLABORATORY REPORTCOMPRESSIVE STRENGTHTESTRHEOLOGYSLURRY DENSITYFREE WATERTESTFLUID LOSSTESTLAB ANALYSISREQUEST

Laboratory Procedures & Equipment

Lab Analysis Request - (LAR)Submit LAR to lab requesting a slurry formulationDesignate additives available for slurry designRequest specific performance parameters;DensityRheology ( PV, YP & Gel Strength)Fluid LossThickening TimeFree WaterCompressive StrengthProvide information on well parametersJob Type, Depth (MD/TVD)Temperatures (BHST/BHCT/maxHCT)Pressure Profiles.

Laboratory Analysis ReportAt the conclusion of Cement Slurry formulation and subsequent testing a report is produced outlining the following;Part 1Information requestedSummary of resultsConclusions and recommendationsPart 2Laboratory Tests and ResultsPart 3Appendices as necessary

LAR NumberWell ConditionsSlurry FormulationSlurry PropertiesTypical LAR format generated by LabDB* software

Sample CalculationSample volume for slurry testing is 600 mlConsider the following slurry composed of;Class G Neat & 44% waterCalculate for 600 ml :ratio = Total Volume / 600 ml = 54:1MaterialWeight(lbs)Absolute Volume(gal)Volume(gal)Weight(gram)Volume(ml)Class G Cement940.03823.5942637.713589.6Water 44%41.360.12024.9718760.618813.5TOTAL135.368.5661398.332403.1

Slurry Preparation - API spec 10B Section 5Mixed 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

Slurry Tests - Density & FWDensity Measurement (API Spec 10B Section 6)Pressurized or Atmospheric BalanceUnits are ppg, Kg/m3, SGFree Water Test (API Spec 10 Section 6)Slurry placed in 250ml graduated glass test tubeFree water (ml) measured after 2 hours

Static Fluid Loss - API Spec 10B Section 10Simulates amount of fluid loss under pressure against a permeable formationUse HPHT cell (simulates downhole conditions)DP = 1000psi, 93F>T > 194F (90C)Formation simulated by 325 mesh screenBacked up by a 60 mesh screenConditioning procedures as per Section 10.6 & 10.7Testing procedure as per Section 10.11

Filtrate LossFor slurries that dehydrate in less than 30 minutes, Fluid Loss value is obtained by :

The Relationship

Rheology - API Spec 10B Section 12Correlation between shear stress and shear rateTested with Viscometer (FANN 35)Rotational speed (Shear rate)300 RPM200 RPM100 RPM60 RPM30 RPM600 RPM not used.

Rheology6 RPM and 3 RPM readings omitted.3 RPM reading is used to determine the fluid gel strength at;10 seconds & 10 minutesSlurry CupBOB (Stationary)Rotational Sleeve

Slurry Tests - cont.Determine length of time a slurry remains fluidPressurized consistometer simulates both;TemperaturePressureReported in Bearden units of consistency (BC)Upper fluid limit (API) 100 BCAPI spec 10 for P-T schedules (example Fig B-7 in Well Cementing)Casing, Liners, Squeeze cementingThickening Time

Thickening Time Test CurveTime (min)Temperature deg.FBc10050BcTemp.1002003004005000

API Schedules - API Spec 10B Section 9.5Pressure and Temperatureschedules derived from field dataschedules available for casing, liner and squeeze jobsP-T effect on Thickening Timecontinuous exposure to varying P-T profilesmax P-T not necessarily at same pointTOC will be exposed to max P-T while circulatingNew Instrumentation & Refine ProceduresAPI schedules do not cover all factorsdynamic wellbore simulation tool

Solution - CemCADE

BHCT PredictionBHCTMax HCT

Slurry Tests - Compressive StrengthSet cement strength under downhole conditionsApparatus;Curing Bath (ATM pressure & 82oC)Curing Chamber (3000 psi & 193oC)Procedure.Measurement UnitOther methods

Summary of Test Procedures

Sheet1

Test CategoryEquipmentProcedure Reference

SamplingDiverter Flow SamplerASTM C702, API Spec 10(3) & 10B(4)

Slurry Preparation2-Speed Propeller MixerAPI Spec 10(5) & 10B(5)

Slurry ConditioningAtmospheric ConsistometerSee relevant sections for Free water, Fluid loss and Rheology in API Spec 10 & 10B

Thickening TimeAtmospheric and Pressurized ConsistometerAPI Spec 10(8) & 10B(9)

Static Fluid LossHTHP Fluid Loss CellAPI Spec 10(App F) & 10B(10)

Compressive StrengthWater/cooling Bath, Curing Chamber, Hydraulic Press, UCAAPI Spec 10(7) & 10B(7 and 8)

Free Water250ml graduated glass cylinderAPI Spec 10(6 and App M) & 10B(15)

PermeabilityPermeameterAPI Spec 10(App G) & 10B(11)

RheologyRotational viscometerAPI Spec 10(App H) & 10B(12)

Static Gel StrengthRotational viscometerAPI RP 13B(2) & 10B(12.7)

ExpansionBar mould, Cylindrical sleevesASTM C151

Spacer/Wash/Cement CompatibilityRotational viscometer, Fluid loss cell, Consistometer, Hydraulic pressAPI Spec 10(App P) & 10B(16)

Particle Analysis (Portland Cement)Blaine permeameterASTM C204

Chemical Analysis of Dry BlendsUV absorption spectrophotometryASTM C114

Chemical Analysis of Mix waterWet chemical methodAPI RP 45

Sheet2

Sheet3

Lab ExerciseEquipment introductionFamiliarisation with API Procedures