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CAPEXSavingsandIntegrityEnhancementinGasLiftWellsSurfacePipeworkAllrightsreservedPetroleumTechnologyCompany(hereinafterPTC)2016.Reproduction,distributionorstorageofanykindwithoutthewrittenconsentfromPTCisprohibited.AbstractUntilrecently,ithasbeennecessarytohavetwoseparatepipe-linesconnectedtotheAAnnuluswellheadingasliftedwells. One line for lift gas injection, and one for blow down. This white paper describes the use of field proventechnologies,which can significantly reduce theamountofpipeworkandnumberof valvesnecessary in thewellbayarea. In addition to space-saving, the benefits include: CAPEX savings, improved well integrity, and more reliablepressureandtemperaturedataacquisition.TraditionalGasLiftWellheadPipeworkArrangementThetypical’twoline’arrangementisshownbelowontheLHS.Thiswasnecessarybecauseacheckvalvetypedeviceisusuallyinstalledontheliftgasinjectionline,whichwouldnotpermitblowdown.

SimplifiedGasLiftWellheadPipeworkarrangementThissimplifiedarrangementisshownontheRHSabove.Theenablingtechnologiesarethe:

• MSAS-G: a double integrity barrier, hydraulically actuated wellhead safetyvalve system (withbidirectional flow / fail safe closed functionality similar toa sub-surfacesafetyvalve).• VRSense:adoubleintegritybarrierpressure/temperaturesensor.They are installed in the threaded profiles (VR profiles), which are present in allwellheads (machined into both side outlets). Because the MSAS-G enables bidirectional flow, there is no longer any need for separate injection and blow downlinestothewellhead.ThespareportonthewellheadcanthereforebeusedtoinstalladoublebarrierannulusPressure/Temperaturesensor,whichsignificantly improveswellintegrity.Improveddatareliabilityisalsofacilitated[1].

www.ptc.as 1

Traditional vs Simplified GL Wellhead Pipeline / valve arrangements

P P

P P

Remove •  4 x A Annulus Gate Valves •  1 x B Annulus Gate Valves •  1 x Check Valve •  3 x Instrument flanges and gauges •  Associated Pipework Replace with •  2 VR Sensors / 1x MSAS G

P

Bleed / blow down to flare / drains

Bleed / blow down to flare / drains

Lift Gas Injection

Lift Gas Injection

Primary Barrier Secondary Barrier

MSAS-G

VRSense

Copyright©PetroleumTechnologyCompany2016

CAPEXandOPEXSavingsTheuseoftheMSAS-GandVRSenseeliminatestheneedfor:

• 4xAAnnulusGateValves• 1xBAnnulusGateValve• 1xCheckValve• 3InstrumentFlangesandPressureGauges• AssociatedPipework

This can amount to significantCAPEX savings, especiallywhereCRAmaterials are employedandwhere lengthypiperunstoandfromthevariousmanifoldarerequired.ThelifecycleOPEXcostsforNDT/maintainingthevariousvalves/pipeworkthatcanberemovedareobviouslyalsoeliminated.InapublishedSPEpaper[2]oneOperatingCompanyconcluded:

“In addition to the safety benefits of less facilities subjected to damage from drilling and maintenanceoperations,thereisadirectcostsavingsachievedthroughtheoptimizationofsurfacefacilities.…farexceededthecostofimplementingthenewLiftGasSafetySystem(LGSS)technologyintothefielddevelopment”

WellIntegrityBenefitsAnumberofwell integritybenefitsarealsodelivered.ThewidelyfollowedTheNorsokD10‘Well IntegrityforDrillingandWellOperationsGuidelines’states:

“AlargevolumeofpressurisedhydrocarbongasintheAAnnulirepresentsasubstantialrisk”……"AllgasliftedwellsshallhavetwobarrierstopreventreleaseoftheAannulusgasvolume”

Referringagain to thewelldiagramsoverleaf, it canbeseen thenewapproach facilitates this requirement. It isalsonoteworthythattheprimarybarrierenvelopenowsitswithinthewellbore,whereitisprotectedfromdroppedobjectorcollisiondamage.This is in contrast to the traditional configuration, where only a single barrier exists, some distance away from thewellbore.Thisisparticularlyimportantinsituationswheremultiplewellsareco-locatedinaconfinedplatformorwellpad.Inthesecasesunplannedincidentsduringoperationsonadjacentwells,couldresultindamageto‘singlebarrier’pipeworkcontaininghighpressureliftgas,wherenosecondarymeansofisolationispossible.

Although not the cause of the disaster, thesituation resulted in 4 wells continuing to blowout,viathetubing/casingannulus(AAnnulus),for5 weeks after the original fire was extinguished[3].The reason the fires continued to burn was acombinationof:• The single barrier that the annulus linegate valve offered vs the release of annulus gasfailed, allowing communication between theannuluscontentsandatmosphere.• Thecheckvalvesinthedownholegasliftvalves failed, allowing reservoir fluids to followcontinuouslyintotheannulus.It was after this disaster that the need for adouble barrier to flow from the gas lift annuluswasfirstrecognised.

[1]PTCWhitePaper:AnewApproachtoAnnulusPressureMonitoring:ImprovingDataReliabilityandWellIntegrity,whileReducingLifecycleCosts[2]SPEPaper171748:SurfaceSafetySystemEnhancesGasLiftSafetyandOptimizesSurfaceLineArchitectureonIslandWells[3]FireintheNight,ThePiperAlphaDisaster:SMcGinty