The Properties of Drilling Muds at High Pressures

ThePropertiesofDrillingMudsatHighPressuresandHighTemperaturesAuthor(s):B.J.Briscoe,P.F.Luckham,S.R.RenReviewedwork(s):Source:PhilosophicalTransactions:PhysicalSciencesandEngineering,Vol.348,No.1687(Aug.15,1994),pp.179-207Publishedby:TheRoyalSocietyStableURL::28/11/201121:17YouruseoftheJSTORarchiveindicatesyouracceptanceoftheTerms&ConditionsofUse,[e-mail]ratingwithJSTORtodigitize,preserveandextendaccesstoPhilosophicalTransactions:PhysicalSciencesandEngineering.(bymass)clayparticles.Thethinnedvarietycontainssimilarquantitiesofclayparticlesbutrelativelylargeamountsofelectrolytes.Theinclusionofbariteparticlesinthesesuspensionsisaroutinecommercialmeansofincreasingthedensityofthemedia.Thedatahavebeenobtainedbytheuseofarolling-balltyperheometer,forperformingrheologicalmeasurementsatpressuresupto1400bar(1bar105Pa)andattemperaturesupto140?C.TherheologicalresponseofthesemodeldrillingfluidsisshowntoapproximatetothoseofBinghamfluids.Theexperimentaldata,whicharereportedintermsoftwoBinghamparameters(ayieldstressandaplasticviscosity),showthattheapplicationofhighpressuremodifiestheBinghamcharacteristicparametersinawaywhichisbothtemperatureandmudcompositiondependent.Therheologyofthesemudsisfoundtobeshear-historydependentandtheextentofthiseffectisdescribedintermsofa'tenminutegelstrength'.Thisparameterprovidesameansofquantifyingthethixotropicproperties,orgelrestructuringrate,ofthemuds.Aninducedvolumechangemodel,anapplicationofthelawofCorrespondingStates,hasbeenintroducedtodescribethevariationsoftheBinghamparameters(theyieldstressandtheplasticviscosity)oftheconcentratedmudsasafunctionofpressure,temperatureandclaycontent.Themodelisgenerallyeffectivefortherationalizationofthevariationoftheplasticviscosity.Themodel,however,presumesanequilibriumstateforthesystem,andtherationalizationoftheyieldstressdataonthisbasis,particularlyatlowtemperatures,ismuchlesssatisfactory.Thedatasuggestthatthecharacteristicgelrestructuringtimesarelongcomparedwiththetimescaleofexperimentsandhence,completegelformationmaynothaveoccurredduringthetimescaleofourexperiments,particularlyatlowertemperatures.Hencethefullplasticyieldstrengthpotentialwasnotachieved.Athighertemperatures,itappearsthatthegelstructureismorefullyrecoveredwithintheexperimentaltimescaleandtheinferenceisthereforethatthegelationprocessisthermallyactivated.Thedataalsosuggestedthatthermallyinducedelectrolytedissolutionmayberesponsibleforcertainfeaturesnotedinthetemperaturedependenceoftherheology.Inaddition,thedensitiesandthesonicvelocitiesofthesemudsathighpressuresandhightemperaturesaredescribedanddiscussed.Phil.Trans.R.Soc.Lond.A(1994)348,179-207?1994TheRoyalSocietyPrintedinGreatBritain179Vol.348.A(15August1994)B.J.Briscoe,P.F.LuckhamandS.R.RenNotationATtemperature-dependentcoefficientforyieldstressCfisothermalcoefficientofcompressibilityCfmisothermalcoefficientofcompressibilityofmudsD,ddiametersoftubeandballrespectivelyPpressureSyexponentofyieldstressagainstclaycontentrelationTtemperatureTDcriticalgeldisruptiontemperatureofamudTRcriticalgelrestructuringtemperatureofamudV1volumeofsampleathighpressurehightemperature(HPHT)ambientconditionsV0volumeofsampleatroomambientconditionsVssonicvelocityinfluidVtterminalrollingvelocityofaballOXppressurecoefficientforsonicvelocity:x(0),/P(P)factorsofpackingandcompressibilityYeequivalentshearrateimposedbyarollingballVpl(P,T)plasticviscositymeasuredatpressure,P,andtemperature,T/pi,lplasticviscositymeasuredatroomambientcondition[]pJ]normalizedplasticviscosity0inclinedangleofrollingballrheometerpdensityoffluidPodensityoffluidatroomambientconditionoratreferenceconditionsY]oviscosityatreferencetemperatureYHBhighshearviscositydefinedbyAldermanetal.PPTdensityoffluidatpressureP,temperatureTPsdensityofrollingballq5wclaycontentbymassorclaymassfraction()0volumefractionofsolidparticlesAPwincreaseintheeffectivemassfractionofthebentoniteclaybroughtaboutbyapplicationofanisothermalpressure,comparedwithambientAeq