TrainingonConventional

andSpecialCoreAnalysis

21-25November2016

Rueil-Malmaison,France

OrganizedbyRolandLenormand

Training on CCA and SCAL experiments November 2016

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TrainingonCCAandSCALExperiments

1. OverviewThisdocumentpresentsanexampleofthetrainingprovidedbyCYDAREXonspecial

coreanalysis(SCAL)experiments.

Thetrainingcoversthefollowingtopics:

• Gaspermeability/porosity-->notionofrocktyping

• Formationfactor

• LiquidPermeabilityExperiments

• TracerTestExperiments

• Pc/RIExperiments

• Two-PhaseFlowExperimentsinsteadystate

• Two-PhaseFlowExperimentsinunsteadystate

Allexperimentsaredoneunderlaboratoryconditions,withpressurebelow5bars.

2. Porositymeasurement

Porosityisdefinedas:

VpVt

f = (1)

WhereVpisthevolumeofporesandVtthetotalvolume.Porositycanalsobeen

calculatedusingthevolumeofsolidVssinceVt=Vp+Vs

Vt VsVt-f = (2)

Forcylindricalplugs,thetotalvolumeisderivedfromthelengthLanddiameterD:

2Vt L D / 4= p (3)

AndthevolumeofsolidusingthegraindensitydandthedrymassMdry

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Vs Mdry / d= (4)

Massisdeterminedwithabalance(accuracy0.01g)anddimensionswithacaliper

(accuracy0.01mm)

3. GasPermeabilityExperiments

GaspermeabilityismeasuredwithaTinyPermcommercializedbyVindum

Engineering.

TinyPermisaportablehandheldairpermeameterusedformeasurementofrock

matrixpermeabilityonoutcropsandatthecorescale.

Themeasurementisbasedonthetransientdecayofthepressureinsidethecylinder

whenthevalveisopen.Theapparatusdeliveranumberconvertedinto

permeabilitywithachart.

4. RocktypingForthevarioussamples,permeabilityisplottedasfunctionofporosityinsemi-log

scale.Thetrendscorrespondtothedifferenttypesofrocks,sandstones,carbonates,

doubleporosity…

1.00

10.00

100.00

1000.00

10000.00

0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35

perm

eability(m

D)

porosity(frac.)

FS

GVL

GV

GVX

GVZ

CLA

BRAU

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5. Formationfactor

Theplugsareprovided100%saturatedwithbrine,NaCl35g/l(density r =1.024g/cc).Thedrymassbeforesaturationisknown.

1) PorevolumeisdeterminedfromthedifferenceofmassPv (Msaturated Mdry) /= - r

2) PorosityisdeterminedusingPvandgeometricaltotalvolumeVt: Vp / Vtf =

Formationfactorisderivedfromthemeasurementofelectricalresistivity r oftheplug.Resistanceisgivenfromvoltageandintensity(1000Hzgenerator,1Volt

maximumvoltage)R V / I= andresistivityby:R L /S= r ,whereLislengthandS

surfacearea.Intensityisobtainedmymeasuringthetensionoveracalibrated

resistance(200ohms).

FormationfactorFisdefinedastheratiooftheplugresistivitybythebrine

resistivitygivenbyadiagram(fromSchlumberger).Theresultsareingood

agreementwithArchie’slaw:2F -= f

6. LiquidPermeabilityExperiments

Objective

Measuringthevariationofpressureasafunctionofflowratetomeasurethe

absolutepermeability.

ExperimentalDesign

Coreholder:Rocksamplesaretypically25mmindiameterand40mminlength.

0

0.5

1

1.5

2

2.5

3

3.5

-2 -1.5 -1 -0.5 0

log(Form

ationFactor)

log(porosity)

logff

ArchieSlope-2

redone

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ExperimentalSetup:

ExperimentalProtocol:

Injectionof20g/LNaClbrineatdifferentflowrateQ.MeasurementsofPin;Poutis

atmosphericpressure.

5stepsinQ:0,100,200,300,400,499cc/h.Measure∆Patplateau.Measurements

donewithincreasinganddecreasingflowrateforqualitycontrol.

Here,sampleGVI-4,25mmindiameter,40mminlength.

Results

Q(cc/h) ∆P(bar)atplateau

0 0.0074

100 0.223

200 0.417

300 0.575

400 0.714

499 0.856

400 0.700

300 0.533

200 0.361

100 0.185

Table1:Pressureatplateau.

Interpretation

InterpretationusingmodulePermeabilityinCYDAR,optionSteady-Stateliquid.

Fillin“Information”,“Sample”,“Fluid”,and“DataPoints”.

Then“CalculatePermeability”.Resultscanbeseenin“View”menu.

Q

PoutPin

DP

Q

PoutPin

DPDP

Figure1:Dataacquisitionshowingpressureasafunctionoftime.

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Figure2:permeabilitymeasurementanalyzedinCYDAR.

Finalcalculation:k=124mDarcy.

Troubleshooting

Potentialproblemsandcorrections:

• InertialeffectsifReynold’snumber>1.

• Klinkenbergeffectsforgasifdensityislow.

• Claywithinthesamplecouldmakeithardtoreachasteadypressure.

• Airwithinthesample.

7. TracerTestExperiment

Objective

ATracerTestgivesameasureofthehomogeneityofthesample.Ifthesampleis

heterogeneous,itshouldnotbeusedformeasurementsofrelativepermeability.

ExperimentDesign

Asampleisloadedwith20g/LNaClbrine.Duringinjectionofa50g/LNaClbrine,

theelectricalconductivityofthesolutionatoutputismeasured.Thechangedof

conductivityasafunctionoftimewillgiveinformationontheporesizedistribution.

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Results

RawData:MeasurementsdoneonGP4.

Figure3:50g/Lreplacing20g/L.

Figure4:20g/Lreplacing50g/L.

Interpretation

Figure5:Voltageasafunctionoftime.

Figure6:FirstderivativeusingCydar.

CYDARcurvefittingtoolisusedtofittheexperimentaldatawithasplinefunction,

andcalculatethefirstderivative.Timecanbenormalizedasthetimeneededto

injectoneporevolume.Voltage(ordensity)canbenormalizedbetween0and1.

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Figure7:normalizedvoltagevs.timeandfirstderivative.

Figure8:normalizedvoltagevs.timeandfirstderivative.

Interpretation:

Homogeneoussample(theoretical):spreading<<1porevolume.

Symmetricalcurve:highlyheterogeneousbutnopreferentialpaths.

0

0.5

1

0 1 2 3 4 5

Pore Volume injected

flux

deriv

ativ

e

0

0.5

1

1.5

2

0 1 2 3 4 5

Pore Volume injected

flux

deriv

ativ

e

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Dissymmetricalcurve:highlyheterogeneouswithpreferentialpaths.

Troubleshooting

Ifthesampleisheterogeneous,itshouldnotbeusedformeasurementsofrelative

permeability.

8. Pc/RIExperiments

Objective

Toobtainthecapillarycurve(Pc)curveasafunctionofwatersaturation,andwater

saturationasafunctionofResistivityIndex(RI).

ExperimentDesign

Definitions:

• Drainage:experimentwherewaterispushedwithoil.StartsatSw~1.

• Imbibition:experimentwhereoilispushedwithwater.

• CapillaryPressure:Pc=Poil–Pwater

• ResistivityIndex:RI=R(Sw)/R(Sw=1)=Sw-n

• FormationFactor:quantifyeffectofrockonelectricconductivity

fR=Rrock/Rbrine=σbrine/

σrock

Archie’slawusedforlogcalibration:fR=φ-m

0

0.5

1

1.5

0 1 2 3 4 5

pore volume injectedflu

x de

rivat

ive

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Withφtheporosity;m,Archie’slawexponentorcementationexponent.Foracleanformation,m=2,m<2withclays

Experimentalcell:

ExperimentalSet-Up:

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MeasurementsofResistivity:

Figure9:measurementwith4electrodes.

Figure10:measurementwith2electrodes.

Toavoidcontactresistanceduetooilontheelectrodes,atechniquewith4

electrodesispreferred.

ActualSet-Up:

Thepressureisimposedwiththeairtankontheoilsurroundingthesample.A

porousplateallowsthewatertoexitthesamplebutnottheoil.Foreachpressure

step,thevolumeofwaterproducedandtheresistivityaremeasuredasafunctionof

time.

ExperimentalSimulationusingCYDAR

DeterminingtheoptimumoilpressurestepsusingCYDAR:

Two-PhaseFlowexperiments,PorousplateExperiment,

• Samplesize,samplecharacteristics,fluidcharacteristics,

• oneporousplateinoutlet,

• blocktimes,startswith1dayperstepand5pressuresteps,

• KrisenteredasaCoreyfunction,

• Pcinputisusuallyobtainedfrommercurymeasurements,andiscopy/paste.

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CYDARisusedtosimulatethetimetoreachequilibrium,andthetotalvolumeof

waterproduced.

Theconstraintsaretohaveameasurableproductionofwaterateachstep,anda

maximumpressurebelow5bars.Here,forinstance,weseethatthefirstpressure

stepdoesn’tquitereachequilibriumandshouldbelonger.

ResultsandInterpretation

Productionofwaterasafunctionoftimeisrecorded.Andforeachmeasurement,

thetensionVI,V2,andV4aremeasured.

TheinitialwatersaturationSwwas1;measuringthewaterproducedgivesSwasa

functionoftime,imposedPc,andRI.

Figure11:Imposedpressure(red)andwatersaturation(blue)asafunctionoftime.

Figure12:MeasuredPc(red)comparedtoMercuryPc(blue).

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Figure13:LogRIasafunctionofLogofwatersaturationmeasuredwith2(blue)and4(red)electrodes.

TheexperimentpresentedhereshowsamuchsmallerPc(Figure12)comparedto

whatexpected.Thesampleseemstohaveproducedtoomuchwaterfortheapplied

pressure.

Troubleshooting

• Riskofbreakingtheporousplatewhenclosingthecell.

• Riskofimposinganinitialpressurethatistoohighandemptyingthesample

inonestep.Needforsimulation.

• Makesuretolockthecellwithscrewstoavoidlossofpressureovertime.

9. Two-PhaseFlowExperiments–steadystate

Objective

DeterminingtherelativepermeabilitiesKroilandKrwaterinjectingtwofluids.Oncetheabsolutepermeabilityisdetermined(withaPermexperiment),∆PandVwater

producedareusedtodeterminedKr.

Evaluatingthevolumeofwaterproducediseasiersincethesystemisat

equilibrium,sotheratioofwatertooilindeadvolumecanbemeasured.

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ExperimentDesign

(Oilandwaterfiltersarenow15µm).

ExperimentalSimulationusingCYDAR

NumericalsimulationinCYDARisusedtodeterminetheoilandwaterflowrates,

thedurationtoreachequilibrium,andthecorrespondingwaterandoilproductions

andpressure.

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ForsampleGVI-3,withanabsolutepermeabilityof168mDandaporosityof24%:

Figure14:blocktimesandQWandWO.

Figure15:pressureforeachblocktime.

Figure16:averagewatersaturationforeachblocktime.

Figure17:watersaturationprofileforeachblocktime.

Note:Attheendofmeasurements,possibilitytomakebumps(increaseQOwith

QW=0)tohaveinformationonPcbecausetheprofilesaturationislinkedtothe

capillarypressure.

ResultsandInterpretation

Waterproductionandpressuremeasurementsareusedinhistorymatchingto

determinetheoptimalKr.

Figure18:Relativepermeabilitiesafteroptimization.

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Troubleshooting

! InSCALexperiments,numericalsimulationsarerequiredbymajorcompanies(Shell,Total,Chevron…).

! Moreaccuratesincetheycantakeintoaccounttherealphysics:capillarypressure,gascompressibility,heterogeneities,non-constantinjection

conditions…

! Asqualitycontrol,comparisonbetweenrawdata(pressure,effluents,profiles…)andsimulatedresults.

! Differenceforthefinalsaturation:• withanalyticalcalculation(Figure19,symbols)Sw(final)=0.68

• withnumericalsimulation(Figure19,solidline)Sw(final)=0.80

• Theanalyticalcalculationdoesnottakeintoaccountthecapillaryend

effectandusestheaveragesaturationderivedfromtheeffluentbalance

Figure19:Differencebetweenanalyticalandnumericalresults.

10. Two-PhaseFlowExperiments–unsteadystate

Objective

DeterminingtherelativepermeabilitiesKroilandKrwaterinjectingonefluid,andusingtheshapeofthetransient∆PandwaterproductionVwater.

Eitheronestep(notusedanymore)ormulti-steps.

ExperimentDesign

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Figure20:actualset-up.Adoubleseparatorwithacapacitance is used to record the variation ofwaterlevelwithtime.

Results

Interpretation

JBNinterpretation

"Welge"methodorJBNforanalyticalinterpretationinmono-stepormulti-steps.

AssumesPc=0.Analyzedataafterbreakthrough.

V’=dV/dt.

* *w ow o

LQ LQP ; P

AK AKµ µ

= = ' 'w o w oV V Qt ; V V Q+ = + =

'w w o o PS Si (V tV ) / V= + −

' * ' *o w o o

w oV P V P

Kr (1 ) ; KrQ P t P' Q P t P'

= − =− −

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Exampleofonestep;herebreakthroughisatmaximumpressure(butnotalways).