自均衡地面控制的井下安全阀的可靠性和简化设计的发展
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OTC8199@
DevelopmentofaSelf-EqualizingSurfaceControlledSubsurfaceSafetyValveforReliabilityandDesignSimplification
ThomasG.HillJr.,andRashmiBhavsar,CameoProducts&ServicesCo.
Copyright1996,OffshoreTechnologyConferenceThmpaperwaspreparedforpresentahonattheOffshoreTechnologyConferenceheldmHoustonTexas&9May1996
Thmpaperwasselectedforpresentationby!heOTCProgramCommllfeefollmwngreviewof!nformat{onmntalnedonanabs!ractsubmlledbylheauthor(s)Contentsofthepaperaspre-sented,havenotbeenrewewedbytheOffshoreTechndcgyandaresuL@ltocorrectionbytheauthor(s)Themalenal,aspresented,doesnotnecessarilyreflectanypositionoftheOffshoreTechnologyConference01ItsofhcersPermissmntocopyISrestrictedtoanabstractofnotmoreIhan300wordsIllustrationsmaynotbecopedTheabstractshculdcontaincon-SpiCUOUSacknowledgmentofwhereandbywhomthepapelwaspresented
AbstractSurfaceControlledSubsurfaceSafetyValves(SCSSVS)arenormallycloseddevicesthatprovidecontrolofwellborefluids,andw-crequiredinvirtuallyalloffshorewellsworl(l-wide.Thispaperdescribesself-equalizingSCSSVS,discussestheevolutionofthetechnology,reviewscurrentdesignissues,andoffersarecenttechnologicaladvancethatplacesanequalizingpassagewayinauniqueconfiguration.Proceduresrequiredtoopennon-equalizingSCSSVSarediscussed,aswellasmethodsofprovidinganinternalequalizingpas-sagewayinthevalve,andtheinherentadvantagesanddisadvantagesofeach.
Self-equalizingSCSSVSfeaturinga“through-the-hard-seat”equalizingpmsagewaywillhavewideappliczititminlowtomediumpressureoffshorewellswhereoperationaldifficultiesmayruleoutatraditionalsurfaceequalizingsystem.Theeco-nomicsofmostproducingfieldswillbeenhancedbythelowercost,opemtiortalease,thesimplicityandreliabilityofthisdevelopment.
Performanceofthevalveincycletesting,sandslurrytesting,flowerosiontestingandtemperaturetestingisdiscussedinsummary,
IntroductionThemostcommonSCSSVSonthemarkettodayhaveflapperclosures,andarebiasedclosedbyaninternalspring.Asmalldiametercontrollineconveyshydraulicfluidunderpressurefromasurfacepumptoapistoninternaltothevalve,whichcompressesthespringandholdsthevalveintheopenposition,Lossofcontrollinepressureforanyreasoncausesclosureofthevalve.PressurebuildsbelowtheclosedSCSSV,whilethepressureabovebleedsoff,andapressuredifferentialacrosstheflapperisestablished.
Forseveralreasons,thepressureinallSCSSVSupstreamanddownstreamoftheclosuremustbenearlyequalbeforeopening.Whenthevalveisintheclosedposition,wellfluidpressureactingupontherelativelylargesurfaceareaoftheflappermakesopeningdifficultbecausethehydraulicareaof
theoperatingpistonissmaller.Thisdifficultyinopeningcannotbeeasilyovercomesimplybyincreasinghydrauliccontrolpressure,Themechanicalforceexertedagainsttheflapperbytherelativelysmallcross-sectionalareaoftheopeningpistonandcylinderassemblyissimplyinadequatetoopenthevalveatnormalhydraulicpressures.Increasingthecontrolfluidpressureinanefforttoovercomeclosingforcesmayburstthecontrollinecarryingthehydraulicfluidand/ordamagecriticalinternalparts.Eveniftheflappercouldbeopenedunderadifferential,theinitialflowofwellfluidwoulderodetheprimarysealingsurfaceoftheflapperand/orseat,Anydamagetothisprimarysealingsurfaceisextremelycrit-icalbecauseitmustremainintacttopreventuncontrolledflowofwellfluidswhenthevalveisclosedinanemergency,Toovercomethesedifficulties,mechanismshavebeendevelopedtoallowthepressureaboveandbelowtheflappertoequalizepriortothecompleteopeningoftheflapper,
4712DevelopmentofaSelf-EqualizingSurfaceControlledSubsurfaceSafetyValveOTC8199
forReliabilityandDesignSimplification
Whyself-equalizing?Historically,self-equalizingsafetyvalveshavebeenjustafractionalpartoftheentireSCSSVmarket.Bydesignanddefinition,everyself-equalizingSCSSVonthemarkettodayintroducesanadditionalflowpathpastthevalve’sprimaryclosuremechanism,whichinterjectsanadditionalriskfactorthatmanyoperatorshavebeenunwillingtotake.However,useofthesevalveshasincreasedinthelasttwoyearsastheresultoftwodrivingforcesinmarketconditions.Thefirstisoperatingcompaniesmandatetoreduceproductioncosts.Equalizingvalves,whiletheinitialpurchasecostisgreater,savemoneybysimplifyingsurfaceoperationsduringroutinefunctionalverificationandmainte-nance.
Toequalizeawellwhereastandard,non-equalizingvalveisinplace,apipingsystem,orwelljumpers,orsurfacepumpsmustbeactivatedtobackfillthetubingdownstreamoftheclosurewithpressurebeforethevalvecanbeopened.Routinemain-tenanceofthistypeusuallyoccursonamonthly,orquarterlybasis.Withanequalizingvalve,oneactuatoronacontrolpanelisallthatisnecessarytobegintheequalizationandopeningprocess.