FunctionalIntegrityofNaturalGasStorageinDepletedHydrocarbonReservoirsandAquiferReservoirs

APIRECOMMENDEDPRACTICE1171

SECONDEDITION,NOVEMBER2022

AmericanPetroleumInstitute

ii

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Copyright◎2022AmericanPetroleumInstitute

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Q:120008749

Foreword

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V

Contents

Page

1Scope 1

2NormativeReferences 1

3Terms,Definitions,Acronyms,andAbbreviations 3

3.1TermsandDefinitions 3

3.2AcronymsandAbbreviations 8

4GeneralPrinciplesofUndergroundNaturalGasStorageinDepletedHydrocarbonReservoirsandAquifer

Reservoirs 8

4.1Genera 8

4.2FunctionsofUndergroundNaturalGasStorage 8

4.3HistoryofUndergroundNaturalGasStorageinDepletedHydrocarbonReservoirsandAquifer

Reservoirs 9

4.4GeotechnicalAspectsofUndergroundNaturalGasStorage 9

5FunctionalIntegrityintheDesignofNaturalGasStorageReservoirs 10

5.1Genera 10

5.2GeologicalReservoirCharacterization 10

5.3ReservoirEngineeringCharacterization 11

5.4ContainmentAssuranceofStorageDesign 12

5.5Environmental,Safety,andHealthConsiderationsinDesign 13

5.6Recordkeeping 13

6FunctionalIntegrityintheDesignandConstructionofNaturalGasStorageWell 14

6.1Genera 14

6.2WellheadEquipmentandValves 14

6.3WellCasingandTubing 15

6.4CasingCementingPractices 17

6.5WellBarriers 20

6.6CompletionandStimulation 21

6.7WellRemediation 2

6.8WellClosure(PluggingandAbandonment) 23

6.9Environmental,Safety,andHealth 24

6.10TestingandCommissioning 24

6.11MonitoringofConstructionActivities 25

6.12Recordkeeping 26

7FunctionalIntegrityoftheNaturalGasStorageReservoirandWellsEstablishedandDemonstratedThrough

InitialAttainmentofMaximumReservoirPressureandTotalInventory 30

7.1Genera 30

7.2TestingandCommissioning 30

7.3ReservoirIntegrityMonitoring 30

7.4MechanicalIntegrityMonitoring 31

7.5Recordkeeping 31

8RiskManagementforGasStorageOperations 32

8.1Genera 32

8.2RiskManagementProgram 3

8.3DataCollectionandIntegration 35

8.4ThreatandHazardIdentificationandAnalysis 35

Contents

vi

Page

8.5PreventiveandMitigativeMeasures 40

8.6PeriodicReviewandReassessment 4

8.7RecordkeepingandDocumentation 45

9ntegrityDemonstration,Verification,andMonitoringPractices 45

9.1Genera 45

9.2Overview 45

9.3WellIntegrityDemonstration,Verification,andMonitoring 45

9.4ReservoirIntegrity 47

9.5GasInventoryAssessment 48

9.6Flow,Pressure,andInventoryMonitoring 49

9.7IntegrityNonconformanceandResponse 49

9.8Recordkeeping 49

10SiteSecurityandSafetyPrograms 50

10.1Genera 50

10.2SiteSecurityProcessesandProcedures 50

10.3SiteInspections 51

10.4EmergencyPreparedness/EmergencyResponse 52

10.5CyberSecurity 53

11ProceduresandTraining 53

11.1Genera 53

11.2ManagementofProcedures 53

11.3OperationsandMaintenance 54

11.4WellWork 54

11.5OtherWellEntryandWellOperationProcedures 55

11 IInnt

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11.8SafetyandEnvironmentalPrograms 56

11.9PublicAwarenessandDamagePrevention 57

11.10ManagementofChange 57

11.11Training 57

11.12Records 58

AnnexA(informative)TubularConnectionTypesandFeatures 60

Bibliography 61

Figures

1FlowchartofDocumentSections 2

2RiskManagementProgramFlowchar 33

Contents

vii

Page

Tables

1PotentialThreatsorHazardsandConsequences 37

2PreventiveandMitigativeMeasures 41

A.1TubularConnectionTypesandFeatures 60

1

FunctionalIntegrityofNaturalGasStorageinDepletedHydrocarbonReservoirsandAquiferReservoirs

1Scope

ThisRecommendedPractice(RP)appliestonaturalgasstorageindepletedoilandgasreservoirsandaquiferreservoirs,andfocusesonstoragewell,reservoir,andfluidmanagementforfunctionalintegrityindesign,construction,operation,monitoring,maintenance,anddocumentationpractices.Thescopedoesnotincludepipelines,gasconditioningandliquidhandling,compressors,andancillaryfacilitiesassociatedwithstorage.Storagedesign,construction,operation,andmaintenanceincludeactivitiesinriskmanagement,sitesecurity,safety,emergencypreparedness,andproceduraldocumentationandtrainingtoembedhumanandorganizationalcompetenceinthemanagementofstoragefacilities.ThisRPembodieshistoricalknowledgeandexperienceandemphasizestheneedforcase-by-caseandsite-specificconditionalassessments.

ThisRPappliestobothexistingandnewlyconstructedfacilities.However,Section5andSection7applytonewfacilities,andfacilitiesundergoingsignificantexpansion.Section6appliestonewwellconstructionandremediationofaneworexistingwell.SpecificportionsofSection5andSection6maybeapplicabletoexistingreservoirsandwellsasriskanalysis,theavailabilityofnewdata,orotherinformationorconditionsoverthelifeofthefacilitywarrantsre-assessment.Figure1providesachartshowingtheflowoffunctionalintegrityassuranceactivitiesthroughthedesign,operation,andmaintenanceofstoragefacilities,withreferencestothesectionswithinthisRPcontainingguidanceforthoseactivities.Applicabledistinctionsforaquiferfacilitiesareidentifiedwithineachsectionasnecessary.Theterm"Replacement,"asusedinthisdocument,referstothecompletereplacementofafacilityunit,as,forexample,whenanexistingwellisabandonedandreplacedwithanewwell.Thisdocumentrecommendsthatoperatorsmanageintegritythroughmonitoring,maintenance,andremediationpracticesandapplyspecificintegrityassessmentsonacase-by-casebasis.

ThecontentsofthisRParenotallinclusiveorintendedtoreplacetheutiizationofdetailedinformationandproceduresfoundintextbooks,manuals,technicalpapers,orotherdocuments.

Thisdocumentisintendedtosupplement,butnotreplace,applicablelocal,state,andfederalregulations.

2NormativeReferences

Thefollowingdocumentsarereferredtointhetextinsuchawaythatsomeoralloftheircontentconstitutesrequirementsofthisdocument.Fordatedreferences,onlytheeditioncitedapplies.Forundatedreferences,thelatesteditionofthereferenceddocument(includinganyaddenda)applies.

APIRecommendedPractice5A3,RecommendedPracticeonThreadCompoundsforCasing,Tubing,LinePipe,andDrillStemElements

APIRecommendedPractice5C1,RecommendedPracticeforCareandUseofCasingandTubing

APITechnicalReport5C3,TechnicalReportonEquationsandCalculationsforCasing,Tubing,andLinePipeUsedasCasingorTubing;andPerformancePropertiesTablesforCasingandTubing

APISpecification5CT,SpecificationforCasingandTubing

APIRecommendedPractice1170,DesignandOperationofSolution-minedSaltCavernsUsedforNaturalGasStorage

2APLRECOMMENDEDPRACTICE1171

Startintegrityevaluationforthedesign,

commissioning,andoperationofnew&existingoil&gasreservoirandaquiferstoragefieldsandwells

Existing

field/well

Building

newfield/

wells?

Newfield,newwells)orinareaseinmaxPand/orV

No

Yes

Conductreservoirdaracterization&developreservoirdesign(Section5)

Developwell

design

(Section6)

Developsecurity,safety,&

emergencyplans

Re-assessmentofisk.geologiounderstandingandsecuity/safety

(Section10)

plansasrequirediterativelyduningthereservoiriwelldesign

ConductRisk

Analysis

(Section8)

Preventive&

mitigative

measures(Section

8Table2)

Storagefield&welldesign,O&Mprocedures,etc

Revised/updateddesign,O8M

procedures,etc

Fisks

No

monitoredormitigated?

Yes

Develop

procedures,training,&records (Section11)

Developfield,drill&

comp.wellsand/or

increasemax

pressure&volume

Section6and7)Dataand

records

ConductRiskAnalysis

Paiodcreasessmetdrisk,gedogcundastandngsecuitykaeypas,poeduestaning

(Section8)

Rsks

monitoredor

mitgated?

No

Updatereservoir

characterization&

welldesign

(Sections5&6)

Review&update

security,safety,&emergency

procedures(Section10)

Review&update

procedures,training,

&records

(Section11)

Well&reservoir

integrityevaluation

&demonstration

(Section9)

Well&fieldintegritydesign,integrity

statusassessment,integrity

monitoringprograms,&schedules

Figure1-FlowchartofDocumentSections

FuNCTIONALINTEGRITYOFNATURALGAsSTORAGEINDEPLETEDHYDROCARBONRESERVOIRSANDAouEFERRESERVORS3

3Terms,Definitions,Acronyms,andAbbreviations

3.1TermsandDefinitions

Forthepurposesofthisdocument,thefollowingtermsanddefinitionsapply.Thedefinitionsemphasizetheuseofthetermsinthecontextoffunctionalintegrity.

3.1.1

abnormaloperatingcondition

Conditionidentifiedbytheoperatorthatmayindicateamalfunctionofacomponentordeviationfromnormaloperationsthatmay:

—indicateaconditionexceedingdesignlimits;or

—resultinahazard(s)topersons,property,ortheenvironment;or

—indicateapotentialdownholeproblemnotrelatedtodesignorhazard(s)butthatmayrisktheintegrityofthewelorthereservoir.

3.1.2

aquiferpressure

Currentpressureintheinfinite-actingaquiferattachedtoanaquiferstoragereservoiratadistancenotinfluencedbythestorageoperationandtowhichagasstoragereservoirwouldeventuallyreturnifgivenalongenoughshut-inperiod.

3.1.3

aquiferreservoirstorage

Porousandpermeablerockmediaoriginallyfilledwithwaterandconvertedtogasstorage.

3.1.4

areaofreview

Theundergroundgasstoragereservoirandallwellsassociatedwithit,aswellasallnon-associatedsubsurfaceorsurfacestructures,formations,oractivitiesproximalenoughthatcouldimpactorbeimpactedbytheundergroundgasstoragefacilitiesandoperationprocess.

NOTEAreaofreviewincludesthebufferzone.

3.1.5

aslowasreasonablypracticable

ALARP

ReducingrisktoalevelwhichisALARPinvolvesobjectivelydeterminingthebalancewheretheeffortandcostoffurtherreductionmeasuresbecomesdisproportionatetotheadditionalamountofriskreductionobtained.

3.1.6

average(shut-in)reservoirpressure

Pressureofthereservoirbasedonanaverageofwellpressuresinashut-inconditionofnoactiveinjectionorwithdrawalofstoragegas.

NOTEDuetothedynamicpressureconditionsinatypicalgasstoragereservoiroroperationallimitationsonfieldshut-inperiods,theaveragereservoirpressurecanbeextrapolatedorassumedbasedonwellpressuresfromakeyindicatorwell(s)(seekeyindicatorwell).

3.1.7

basalrock

Horizontalrocklayer(s)thatformsaseal(barrier)tofluidflowintheverticaldirectionatthelowerboundaryofastoragereservoir.

4APLRECOMMENDEDPRACTICE1171

3.1.8

basegas

Volumeofgasneededinastoragereservoirtomaintainreservoirpressuretocycletheworkingstoragevolumeandmeetrequireddeliverabilityrates.

NOTEAlsocommonlyreferredtoascushiongas'or"cushiongas"or"padgas".

3.1.9

bufferzone

Areaorintervaloutsidethedefinedgasstoragereservoir,horizontallyandvertically,toprovideprotectionofthestoragereservoirfromencroachmentsandlosses.

NOTEBufferzonesaccommodategeologicuncertaintiesintheexactlocationofthestoragereservoirboundaries.

3.1.10

caprock

Rocklayer(s)actingastheverticalseal(barrier)preventingmigrationoffluidsattheupperboundaryofthestoragereservoir.

3.1.11

caprockthresholddisplacementpressure

Minimumpressuredifferencebetweenthegaspressureatthefaceofthecaprockandthewaterphasepressureimmediatelyabovethegas-waterinterfacewithinthecaprock,atwhichthegasstartstomovecontinuouslythroughthecaprock.

3.1.12

cementplug

Cementthatisplacedinthewellborewithadefinedbottomandtoptoachievezonalisolationwithinthewellboreandtopreventcommunicationoffluidsbetweenzonesbyprovidingamechanicalseal.

3.1.13

collectorformation

Aformation,usuallyverticallyabovethegasstoragereservoir,capableoftrappingandaccumulatinggas.

3.1.14

communication

Fluidmovementinfluence,whichmaybedetectedbypressureobservation,fluidphysicalandchemicalcompositionanalysistechniques,orothermeans.

3.1.15

consequence

Outcomeofaneventaffectingobjectives.

3.1.16

containment

Abilityofareservoirtoconfinestoredgasandpreventmigrationeitherlaterallyorverticallyoutofthereservoir.

3.1.17

contractorpersonnel

Personorentityusedbytheoperatorbutnotdirectlyemployedbytheoperator.

3.1.18

encroachment

Intrusionofanon-storagewelloroperationsintothedefinedsurfaceorsubsurfacestorageareathreateningtheintegrityofthestorageoperations.

FUNCTIONALINTEGRITYOENATURALGAsSTORAGEINDEPLETEDHYDROCARBONRESERVOIRSANDAouIEERRESERVORS5

3.1.19

functionalintegrity

Totalreliabilityofthestoragesystem,includingthephysicalintegrityofthereservoirandwellcomponentsandtheperformancereliabilityassuranceestablishedbymanagementsystemsemployedbythestorageoperator.

3.1.20

groundwater

Subsurfacefreshwater,potablewater,orwaterthatisorcanbepotentiallyusedasadrinkingwatersupply.

3.1.21

hazard

Asituationorconditionthathasthepotentialtocauseloss,damage,orharmtoastoragewell,wellsite,orreservoirandthusaffectthefunctionalintegrityofthestorageoperation.

3.1.22

inventoryverification

Procedureforconfirmationoraccountingoftotalgaspresentwithinthestoragereservoiratagiventimetoreconcilewithmeasuredvolumesandtotalinventory.

3.1.23

inventory,total

Totalgasvolumewithinthestoragereservoir.

NOTEThetotalinventoryatanygiventimecanbedeterminedbyaninitialdeterminationofgasinplaceandadjustingthatvolumeforproduction,fuel,andfielduseorotherlossesduringproductionoperations;cumulativestorageinjectionandwithdrawalactivity;andstorageoperationsfuel,fielduse,orotherlossesandadjustments.

3.1.24

keyindicatorwell

Shut-instoragewellthatisrepresentativeoftheaveragereservoirpressureoftheactivegasstoragearea.

NOTEKeyindicatorwellpressurecanbeusedtodevelopthepressure-inventoryrelationshipofthegasstoragereservoir.

3.1.25

maximumcyclingcapacity

Maximumamountofworkinggasvolumeabletobewithdrawnandinjectedoverthetimeofacompletedesigncyclefrommaximumtominimumpressureswithinthereservoir.

3.1.26

maximumreservoirpressure

Averagestabilizedshut-inreservoirpressureatmaximumdesigncapacityofgasinstorage

3.1.27

mechanicalintegrity

Qualityorconditionofawellinbeingstructurallysoundwithcompetentpressuresealsbyapplicationoftechnical,operational,andorganizationalsolutionsthatreducetheriskofuncontrolledreleaseofformationfuidsthroughoutthewelllifecycle.

3.1.28

mechanicalintegritytest

Pressuretestthatobtainsdatathatdemonstratesifawellismechanicallyfitforserviceandcapableofstoringnaturalgaswithindesignlimitations.

3.1.29

minimumreservoirpressure

Averagestabilizedshut-inreservoirpressureatminimumdesigncapacityofgasinstorage.

6APIRECOMMENDEDPRACTICE1171

3.1.30

nativegas

Unproducedgasindigenoustothereservoirthatremainsinthereservoiratthetimeofconversiontostorage.

3.1.31

observationwell

Wellthatfunctionsasapressureandfluidmonitoringpoint,locatedwithin,aboveorbelow,orlaterallyadjacenttotheactivestoragereservoir,andgenerallynotusedtoinjectorwithdrawstoragegas.

3.1.32

plan

Documentedexplanationofthemechanismsorproceduresusedtoimplementaprogramandtoachievecompliancewithstandards.

NOTEAspecificwellworkplanfordriling,completion,servicing,orworkoveroperationscanbewritenstep-by-stepinstructionsandassociatedinformation(cautions,notes,warnings)thatdescribehowtosafelyperformatask.

3.1.33

pound-days

Empiricalmethodofestimatingtheaquiferresponsetogasinjectionandwithdrawalcycling.

NOTE1Netpound-daysarecalculatedbysummingthedifferencesindailyreservoirpressure,inpoundspersquareinch,above(plus)orbelow(negative)theaquiferpressureovertheperiodofaninjectionandwithdrawalcycle.

NOTE2Thepound-dayscalculationcanbeusedinhydrocarbonreservoirstorageapplicationsaswellasaquiferreservoirstorageapplications.

3.1.34

pressurecycling

Cyclicvariationsinreservoirpressureduetotheinjectionandwithdrawalofgas.

NOTEInreservoirgasstorageoperations,pressurecycingoftenoccursoveraone-yearperiodwithinjectionsinthesummerandwithdrawalsinthewinter;however,storageoperationsmayinvolveanynumber,timing,andamplitudeofpressurecycles.

3.1.35

pressure-inventoryrelationship

Correlationbetweenreservoirpressureandtotalgasinventoryovertime.

NOTEThedatatotrendtherelationshipcanbederivedfromwellpressureobservationsandtotalinventory.

3.1.36

procedure

Documentedexplanationofactiontakentoachievethestepsofaprocess.

NOTEProcedurescanbeadescriptionoftheexecutionoftasksinamethodorlinkedsetofmethodsthatwllenabletheactivitytobeaccomplishedaccordingtoasetofguidelinesandstandards.

3.1.37

process

Systematic,orderedseriesofeventsdirectedtosomeendthatcompriseanapproachormethodologytoachieveanobjective.

NOTEAprocesscandescribeworkflowactivityandqualitystandardsforawiderangeofprocedures.

3.1.38

program

Overallapproachtomanageafunctionalactivityorphysicalpartofanasset.

FuNCTIONALINTEGRITYOFNATURALGAsSTORAGEINDEPLETEDHYDROCARBONREsERVOIRSANDAouEERRESERVORS7

NOTEAprogramcanbeadefinedoutineofworkactivitiesthataredesignedtoaddressspecificobjectives.Programsidentifywhattodoandwhyitneedstobedone.Theprogramcandefineimportantaspectssuchaspurposeandscope,rolesandresponsibilities,tasksandprocedures,andanticipatedresultsandworkproducts.

3.1.39

risk

Theconsequence'sseverityofarealizedthreatmultipliedbythelikelihoodofitsoccurrence.

3.1.40

riskanalysis

Processtocomprehendthenatureofriskandtodeterminethelevelofrisk.

3.1.41

riskassessment

Overallprocessofriskidentification,riskanalysisandriskevaluation.

3.1.42

riskevaluation

Processofcomparingtheresultsofriskanalysiswithriskcriteriatodeterminewhethertheriskanditsmagnitudeisacceptableortolerable.

3.1.43

riskidentification

Processoffinding,recognizing,anddescribingrisks.

3.1.44

riskmanagementprogram

Coordinatedactivitiestodirectandcontrolanorganizationwithregardtorisk

3.1.45

safeworkpractices

Writenmethodsoutlininghowtoperformataskwithminimumrisktopeople,equipment,materials,environment,andprocesses.

3.1.46

spillpoint

Pointorareainahydrocarbontrapatwhichthetrapcanbebreached.

NOTEThespillpointmayberelatedtogeologicstructure,permeability,fuiddensity,pressure,andviscosity,oranycombinationofthosefeatures.

3.1.47

threat

createdbyanencounterwithoranactivationofahazardduringthestorageoperation

3.1.48

wellhead

Assemblageofsurfaceequipmentusedtomaintaincontrolofthewellandtopermitaccessintothewellbore.

3.1.49

workinggas

Volumeofgasinthereservoirabovethedesignedlevelofbasegas.

NOTEAlsocommonlyreferredtoastopgas"or"currentgas".

8APLRECOMMENDEDPRACTICE1171

3.1.50

zonali