采油化学Word格式.docx

采油化学Word格式.docx

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Theseparatedsaltwaterstillcontainscertainamountsofresidualoil,wherenowpreferentiallyoil-in-wateremulsionsareformed.Theseparationoftheresidualoilisnecessaryinoilfieldwaterpurificationandtreatmentforecologicandtechnicalreasons,becausethewaterisusedforsecondaryproductionbywaterflooding,andresidualoilvolumesinthewaterwouldincreasetheinjectionpressure.

Thepresenceofwater-in-oilemulsionsoftenleadstocorrosionandtothegrowthofmicroorganismsinthewater-wettedpartsofthepipelinesandstoragetanks.Attherefinery,beforedistillation,thesaltcontentisoftenfurtherreducedbyasecondemulsificationwithfreshwater,followedbydemulsification.Crudeoilswithhighsaltcontentscouldleadtobreakdownsandcorrosionattherefinery.Theobjectofusinganemulsionbreaker,ordemulsifier,istobreaktheemulsionatthelowestpossibleconcentrationand,withlittleornoadditionalconsumptionofheat,tobringaboutacompleteseparationofthewaterandreducethesaltcontenttoaminimum.

Thereareoil-solubledemulsifiersandwater-solubledemulsiflers,thelatterbeingwidelyused.Emulsionsarevariableinstability.Thisvariabilityislargelydependentonoiltypeanddegreeofweathering.Emulsionsthathavealowstabilitywillbreakeasilywithchemicalemulsionbreakers.Brokenemulsionswillformafoamlikematerial,calledrag,whichretainswaterthatisnotpartof

thestableemulsions.Themosteffectivedemulsifiermustalwaysbedeterminedfortheparticularemulsion.Demulsifiersareoftenaddedtotheemulsionatthewellheadtotakeadvantageofthetemperatureofthefreshlyraisedemulsiontohastenthedemulsificationstep.

Waterflooding

Duringimprovedoil-recoveryprocesses,waterfloodingoftheoilisapplied.Theentrainedwaterformsawater-in-oilemulsionwiththeoil.Inaddition,saltssuchassodiumchloride,calciumchloride,andmagnesiumchloridemaybedissolvedintheemulsifiedwater.

OilSpillTreatment

Demulsifiers（specifically,oilspilldemulsifiers）canbeappliedtooilspillsinlowconcentrations.Theypreventmousseformationforsignificantperiodsoftimeandcausealargereductioninoil-waterinterfacialtension.Thebestofthesewasfoundtopreventemulsificationatdosagesaslowas1partinhibitorto20,000partsoffreshoilat20°

C[273].Atdosagesof1:

1000,attemperatureshigherthan10°

C,thechemicalalsoresultsinsignificantandrapiddispersionoftheoil.Forverylowtemperaturesorhighlyweatheredoil,theperformanceofthechemicalfallsoffsharply.

DesiredProperties

Demulsifiersforcrudeoilemulsionsshouldmeetthefollowingproperties:

•RapidbreakdownintowaterandoilwithminimalamountsofresidualWater•Goodshelflife•Quickpreparation

MechanismsofDemulsifieation

StabilizationofWater-OilEmulsions

Thestabilizationofwater-oilemulsionshappensasaresultoftheinterfaciallayers,whichmainlyconsistofcolloidspresentinthecrudeoil—asphaltenesandresins.Byaddingdemulsifiers,theemulsionbreaksup.Withwater-solubledemulsifiers,theemulsionstabilizersoriginallyinthesystemwillbedisplacedfromtheinterface.Inaddition,achangeinwettingbytheformationofinactive

complexesmayoccur.Conversely,usingoil-solubledemulsifiers,themechanism,inadditiontothedisplacementofcrudecolloids,isbasedonneutralizingthestabilizationeffectbyadditionalemulsionbreakersandthebreakupresultingfrominterfaceeruptions.

InterfacialTensionRelaxation

Theeffectivenessofacrudeoildemulsifieriscorrelatedwiththeloweringoftheshearviscosityandthedynamictensiongradientoftheoil-waterinterface.Theinterfacialtensionrelaxationoccursfasterwithaneffectivedemulsifier.Shortrelaxationtimesimplythatinterfacialtensiongradientsatslowfilmthinningaresuppressed.Electronspinresonanceexperimentswithlabeleddemulsifiersindicatethatthedemulsifiersformreversemicellelikeclustersinthebulkoil.Theslowunclusteringofthedemulsifierattheinterfaceappearstobetherate-determiningstepinthetensionrelaxationprocess.

PerformanceTesting

Thetrial-and-errormethodofchoosinganoptimaldemulsifierfromawidevarietyofdemulsifierstoeffectivelytreatagivenoilfieldwater-in-oilemulsionistime-consuming.However,therearemethodstocorrelateandpredicttheperformanceofdemulsifiers.

SpreadingPressure

Theperformanceofdemulsifierscanbepredictedbytherelationshipbetweenthefilmpressureofthedemulsifierandthenormalizedareaandthesolventpropertiesofthedemulsifier.Thesurfactantactivityofthedemulsifierisdependentonthebulkphasebehaviorofthechemicalwhendispersedinthecrudeoilemulsions.Thisbehaviorcanbemonitoredbydeterminingthedemulsifierpressure-areaisothermsforadsorptionatthecrudeoil-waterinterface.

CharacterizationbyDielectricConstant

Thedielectricconstantcanbeusedasacriterionforscreening,ranking,andselectingdemulsifiersforemulsionbreaking.Inastudy,thedielectricconstantsofemulsionsanddemulsifiersweremeasuredusingaportablecapacitancemeter,andbottletestswereconductedaccordingtotheAPIspecification.Theresultsshowedthatthedielectricconstantscanbeusedeffectivelytoscreenandrankdemulsifiers,whereasaconfirmatorybottletestshouldbeconductedonthebestdemulsifierstoassistintherapidselectionofthemosteffectivedemulsifier.

ShakerTestMethods

AstudybyEnvironmentCanadaandtheU.S.MineralsManagementServiceattemptedtodevelopastandardtestforemulsionbreakingagents[586].Ninetypesofshakertestmethodsweretried.Althoughtheresultsarecomparablewithdifferenttests,astablewater-in-oilemulsionmustbeused

toyieldreproducibleresults.Testswithunstableemulsionsshowednonreproducibleandinconsistentresults.

ViscosityMeasurements

Watercontentandviscositymeasurementsincertainsystemsshowacorrelationtoemulsionstability.Theviscosityprovidesamorereliablemeasureofemulsionstability,butmeasurementsofthewatercontentaremoreconvenient.Mixingtime,agentamount,settlingtime,andmixingenergyimpact

theeffectivenessofanemulsifier.

Screening

Withoutknowingthestructureindetail,nuclearmagneticresonance（NMR）informationcanbecompiledby13Conthestructureusingthechemicalshifts.Thechemicalshiftscanbecorrelatedwithotherdata,suchasbottletests,andevaluatedbystatisticalmethods.Inaseriesofexperimentalwork

usingprincipalcomponentanalysis,NMRdataandbottletestdatawereusedtoclustermorethan100demulsifiersintoonlyafewdistinctlydifferentchemicalgroupsascharacterizedbytheNMRdata.Similarchemicaltypeshadsimilardemulsificationperformance,whichmeansthatdemulsifierevaluationscanbemadebasedondemulsifierchemistry.Onlyafewofthedistinctlydifferent

emulsifiersneedtobetestedbeforetheoptimizationprocedeurecanstart.BecausethechemicalcharacterizationbyNMRimagingtakesonlyafractionofthetimeofabottletest,itispossibletomorerapidlyfocusonoptimizingthedosageofthedemulsifier.

ClassificationofDemulsifiers

Thechemicalsusedasdemulsifierscanbeclassifiedaccordingtotheirchemicalstructureandtheirapplications.Withthelatterrespect,amaindivisionforwater-in-oilandoil-in-waterapplicationsexists.Furthermore,thedemulsifierscanbeclassifiedaccordingtotheoiltypeused.Fromtheviewofchemicalclassification,twomajorgroupsexist:

•Nonionicdemulsifiers•Ionicdemulsifiers.

CommonPrecursorChemicals

Polyalkyleneoxidesaresubstancesofthefollowinggeneralstructure:

Themostimportantadditivesarepolyethyleneoxide,polypropyleneoxide,andpolybutyleneoxide.Theyarealsoreferredtoaspolyalkyleneglycols,butthisnameiscorrectstrictlyforderivativesof1,2-diols.Polypropyleneoxidehasamolarmassof250to4000Dalton.Thelowermolecularhomologuesaremisciblewithwater,whereasthehighermolecularpolypropyleneoxidesaresparinglysoluble.Theyareformedbythepolyadditionof,forexample,propyleneoxidetowaterorpropanediol.Thesimplestexamplesaredi-andtri-utetrapropyleneglykol.Therearealsoblockcopolymersfromethyleneoxideandpropyleneoxide.Polytetramethyleneglycol（polytetrahydrofuran）isformedbyringopeningpolyetherificationoftetrahydrofuran.Branchedpolyalkyleneoxidesareformedusingpolyfunctionalalcoholssuchastrimethylolpropaneandpentaerythrite.Theproductsareliquidsorwaxesdependingonthemolarmass.Polyalkyleneoxidesareoftenprecursorsfordemulsifiers.

Polyaminesareusuallyopenchaincompoundswithprimary,seconda