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SPE168115CouldEmulsifiedFrictionReducersPreventRobustFrictionReduction?KristenM.Tucker,SPE,FTSInternationalandPaulM.McElfresh,SPE,FTSInternational*Copyright2014,SocietyofPetroleumEngineersThispaperwaspreparedforpresentationattheSPEInternationalSymposiumandExhibitiononFormationDamageControlheldinLafayette,Louisiana,USA,26–28February2014.ThispaperwasselectedforpresentationbyanSPEprogramcommitteefollowingreviewofinformationcontainedinanabstractsubmittedbytheauthor(s).ContentsofthepaperhavenotbeenreviewedbytheSocietyofPetroleumEngineersandaresubjecttocorrectionbytheauthor(s).ThematerialdoesnotnecessarilyreflectanypositionoftheSocietyofPetroleumEngineers,itsofficers,ormembers.Electronicreproduction,distribution,orstorageofanypartofthispaperwithoutthewrittenconsentoftheSocietyofPetroleumEngineersisprohibited.Permissiontoreproduceinprintisrestrictedtoanabstractofnotmorethan300words;illustrationsmaynotbecopied.TheabstractmustcontainconspicuousacknowledgmentofSPEcopyright.AbstractManyofthefrictionreducersinusetodaydemonstratevariousdegreesofperformancebasedonthetypeofmixingwaterutilized,especiallythoseproductswhicharedesignedasan“emulsion”(Aftenetal.2009;Zelenevetal.2009).Inadditiontomoleculardifferencesbetweenvariouspolyacrylamides,thenatureoftheoilexternalqualitiesofanemulsioncanposechallengestobreaking(orinverting)theemulsions(Aftenetal.2009;Zelenevetal.2009).Thesefactorsdirectlyaffecthydrationratesandaredependentonwaterqualityfactorslikesalinity,dissolvedmaterials,suspendedmaterials,andpH(Aftenetal.2009;Zelenevetal.2009).Therefore,itispostulatedthatifthefrictionreducersareappliedinanotherformsuchasapowderorslurriedpowder,theycouldhaveaninherentbroaderspectrumofapplicabilityandefficiency.Thepurposeofthisstudyistodeterminethedifferencesinperformanceofseveralfrictionreducersinvariouswaterqualitiesinordertodetermineifthetypeofpolymerapplicationenhancesorrestrictstherangeofapplicability.Multiplepolyacrylamidesaretestedindifferentformsincludingoilexternalemulsions,powder,andslurriedpowder.Thesefrictionreducersaretestedonaflowloopinuptofourdifferentwaterqualitiesincludingfreshwater,5%KCl,seawater,andproducedwater.Theresultsofthistestingshowthatsomeoilexternalemulsionsarelimitedtosmallerrangesofapplicablewaterqualities.Thepowderpolyacrylamidesamplehasabroadrangeofapplicability,whiletheslurriedpowdershowscomparableandoftensuperiorperformance,especiallyinpoorwaterquality.Switchingtoaslurriedpowderfrictionreducerwouldenhanceoperationalsimplicityandeconomiesofscalebyeliminatingtheneedforseveralproducts.Thepercentpolymeractivitywouldalsosurpassthatofemulsionswhichcouldultimatelyreducethetotalvolumepumpedand,inturn,cost,emissions,time,andtrucktrafficduetofreight.IntroductionSeveraldifferentapplicationsoffrictionreducersareavailableforslickwaterhydraulicfracturing.Generally,thesefrictionreducersaremadefromhighmolecularweightpolyacrylamidepolymers(Aftenetal.2009;Zelenevetal.2009).Themostcommonapplicationstyleisanoilexternalemulsion.However,thesurfactantpackagespresentintheseemulsionstendtolimitthespectrumofapplicationwhichisdependentonthewaterquality(Aftenetal.2009;Zelenevetal.2009).Waterqualityinhydraulicfracturingvaries.Aswaterqualityshiftsfromfreshwatertoproducedwater,theconcentrationofthevariouscontaminantsfluxuates.Watersalinity,hardness,andpHhaveastrongeffectonthehydrationefficiencyofthesepolyacrylamides(Aftenetal.2009;Zelenevetal.2009).Onegoal,fromanoperationalsimplicitystandpoint,istoidentifyaso-called“silverbullet”frictionreducerthathasexcellenthydrationandperformanceregardlessofthewaterquality.Oilexternalpolyacrylamideemulsionsmaynotbetheavenuetoreachingthisgoal.Therearetwootherapplicationstyles:polyacrylamidepowdersandslurriedpolyacrylamidepowders.Theseareprovingtoshowmuchbetterperformanceinabroadspectrumofwaterqualityconditions.2SPE168115StatementofTheoryandDefinitionsFrictionreducerevaluationsareperformedonaflowloopbymeasuringpressuredropandfluidvelocityalongwiththeflowloopdimensionsinordertocalculatedragreductionwithEq.1andEq.2(Aftenetal.2009):𝑓=! ∙ !! ∙ ! ∙ ! ∙ !!(1)% 𝐷𝑅=!!!!!!!(2)where f = Fanning friction factor Δp = pressure drop d = pipe internal diameter l = length of pipe ρ = fluid density v = fluid velocity DR = drag reduction fn = friction factor of solution fo = friction facture of solvent Sincefrictionreducerperformanceisafunctionofhowwellthepolymerhydrates,itisimportanttoconsiderfactorsaffectinghydration.Thesefactorsincludethepolymerchemistry,suspensionmethods,andwaterquality,i.e.salinity,hardness,TDS,pH,etc(Aftenetal.2009;Zelenevetal.2009).Inthisstudy,thefocusisonanalyzingthesuspensionmethodsandhowthosemayaffecthydrationinvariouswaterqualities.Generally,polyacrylamideisprovidedintheformofanoilexternalemulsionwithasurfactantpackagewhichaidsinreleasingthepolymerfromtheemulsion,allowingittohydrate(Aftenetal.2009;Zelenevetal.2009).Thepolymermayonlyhaveapiperesidencetimeof3-5minutesduetothehighpumpratescommoninslickwaterhydraulicfracturing,sofasthydrationratesareessentialforperformance.Severalfric