Improved Frac Efficiency Using FocusShot Perforating_HFJ_v8

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Improved Frac Efficiency Using FocusShot Perforating Hydraulic Fracturing Journal Page 1 of 9

ImprovedFracEfficiencyUsingFocusShotPerforating

Authors:LarryAlbertandGreggFrasure,Allied-HorizontalWirelineServices

INTRODUCTION

Thispaperwillpresentanewconcept(FocusShot)inperforatinggundesigntailoredspecificallyforfracturingoperations(Sites,USPatent9,145,763B1).Currentperforatinggunsshootjetsperpendiculartothegunbody(andcasing),thuscreatingholesinthecasingandtunnelsthroughthecementedannulusandformation,Figure1.Theseperforatingtunnelsareusuallyevenlyspacedalongtheaxisofthecasingandcanbephasedinmanyconfigurations,themostpopularbeing0°,0-180°and60°.FocusShotconfiguresthegunassemblysothatshapedchargesdisplacedfromcenterareorientedbacktothemid-pointoftheperforatinggunassembly(orientationangleincreasesasdisplacementincreases),thusconvergingtheexplosiveenergyandtheperforatingtunnelsonasingleplaneatthecenteroftheperforatedinterval,Figure2.Withtheexceptionofmodifyingthechargecarriertoholdchargesatanangle,theconvergingFocusShotgun-stringusesthesamecomponentsasaconventionalperforatingassembly.Theconvergingshotconfigurationworkswithmostgunsizes,lengths,shotdensitiesandcanberunin0°,0-180°and60°phasing.Inthispaper,wewillreviewthebackgroundforhorizontalwellperforating,reviewthedesignandtestingoftheFocusShottechnologyandthenpresentfieldtestresultsthatdemonstratethevalueforFracoptimization.

BACKGROUND

Perforatingcementedcasingswithexplosiveshapedchargeshasbeenemployedfordecades.

Overthepastfiftyyears,thetechnologyhasadvancedanddevelopedinresponsetoindustrydemandsfordifferentproductstosolvereservoirandcompletiondesignissues.TheconceptofexplosiveshapedchargeperforatingoriginatedinWorldWarIIwiththebazookadesign.

Figure1–ConventionalPerforating

Figure2–FocusShot(Converging)Perforating

Anexplosiveshapedchargeutilizespowderedexplosivescompressedbehindametalliner(powderedorsolid)intoacase,Figure3.Whentheshapedchargeisdetonated,theexplosioncausesthemetallinertocollapsefromthecenterandflowatextremelyhighvelocitiesperpendiculartothechargecasesurface.Thisjetofhighvelocitymetalcreatesahole(perforation)intheguncarrier,casing,cementannulusandtunnelsintotherockformation.Perforatinggunsaredesignedtocarrymultipleshapedchargesconfiguredinvariableshotdensitiesandphasingdependentupontheapplication.Thedesignoftheshapedchargewilldeterminethediameteroftheentryholeinthecasing,depthofpenetrationintotherockformationandshapeoftheperforationtunnel.

PERFORATINGFORFRACTURING

Muchhasbeenwrittenaboutperforatingforfracturingoptimization(Willingham,etal.1993)includingtheselectionofEHD(entryholediameter),phasing(azimuthaldistributionofchargesaroundthecarrier),shotdensity(perforationsperfoot)andlengthofperforationinterval(cluster)(vandeKetterij,dePater1997).Ithasbeenproventhatperforationdesignhasasubstantialimpactonfracturingefficiencyandperformance(BehrmannandNolte1998).Theperforationsaretheconduitforthefracturingfluidtoexitthesteelcasingandapplypressuretotherockformation.Theidealperforationwouldhavesufficientfrictionandpressuredroptoinsurefluidisevenlydistributedtoeachperforationinthecluster/stage,andcreatetheleastamountoftortuosityinthefracturepath.TheseidealperforationswouldallowtheimmediateinitiationofasingletransversefractureatthePreferredFracturePlane(PFP)ateachperforationclusterwithinastage,Figure4.Itisundesirableformultiplefracturestobe

initiatedintheproximityoftheperforationinterval(cluster),orforaxialfracturingtooccur(Daneshy2014).Multiplefracturesand/or,axialfracturingcanrobenergyfromthefluid,reducefracturewidth,reducethelengthofthefractureandrestricttheplacementofproppantintotheformation.Restrictionsonfluidflowoutsideoftheperforationcanresultinascreen-out.Thiswastrueforverticalwells,butisprovingtobeevenmorecriticalforhorizontalwellcompletions.Foroptimalhorizontalwellcompletions,weprefersingletransversefracturesinitiatedateachclusterwithinthestage,withmaximumlength,Figure5.

Previouswork(Daneshy1973,2009,2014)demonstratedthatthestateofstressina

Figure3–ExplosiveShapedCharge

Figure4–TransverseFracture

boreholeprovidesanaturaltendencyforlongitudinal(axial)fractureinitiation.AccordingtoDaneshy,thisisageometricaleffectandindependentofin-situstressorientation.Becauselongitudinalfracturesarenotperpendiculartotheminimumhorizontalstress,theyneedhigherinitialpressuretoextend.Conventionalperforatingadoptedfromverticalwellcompletionsdoesnotpromotetransversefractureinitiationregardlessofspacingbetweenperforations,orphasingaroundthecasing.Theaxialdistributionofperpendicularperforationtunnelscancreatemultiplefracturesandnarrowpathswithconsiderableturbulenceatthewellbore,resultinginhighwellborepressure.Theresultcanbereducedfracturelengths,higherpumppressures,obstructedproppantpathatthewellboreandpotentialforscreen-outs.

AccordingtoDaneshy(2009),abettermethodforperforatingwouldbetoalignallperforationsineachclusterinasingleplaneperpendiculartotheboreholeaxis,Figure6.Figure6(a)showsa

spiralpeforatingpatterncreatedbya60°phasegunassembly.Figure6(b)showsthoseperforationscollapsedtoasingleplane.Unfortunately,withaperforatinggunassemblyitisimpossibletoaligntheshapedchargesto

perforatethecasingonasingleplane.Explosiveshapedchargesmustbeaxiallydisplacedalongtheguncarrierduetospacelimitationsinsidethegunbodyandtoeliminateexplosiveinterference,thusexplosiveshapedchargeperforationsareaxiallydisplacedalongthecasingcircumference.Whileitisimpossibletoalignalltheexplosiveshapedchargestoasingleplaneinsideaperforatinggunbody,analternativewasproposed(Sites2012).Bychangingtheanglefortheperforatingchargesinsidethegunbodytoorienteachoftheperforationsbacktothecenterofthegunassemby,theperforationenergyandtunnelscanbeconvergedtoasingleplane,Figure7.Theperforatingtunnelswillconvergeatadistancefromthecasingdependinguponshaped

Figure5–StageFracturing

Figure6–PerforationGeometry

Figure7–FocusShot60°Phasing

geometricorientationandtargetpenetration(i.e.deeppenetratingchargessetatahigheralignmentanglewillconvergedeeperintothereservoirrock).

DEVELOPMENTANDBALLISTICTESTING

Totesttheperformanceoftheconverging(FocusShot)concept,aseriesofballistictestswereperformedinconcretetargetsatashapedchargeperforatingtestingfacility.Thetestsweredesignedtoevaluategunstability,chargeperformance(interference),targetpenetration,casingintegrityandperforationexitholediameters.Thetestwassetuptoshootaseriesofoneandtwoft.long,3.125in.ODperforatinggunsloadedwithstandardshapedchargesalignedatvaryingangles,Figure8,intofiveft.

diameterflowerpotconcretetargetswith4.5in.ODcasingcentered,Figure9.TheFocusShot(converging)configurationwastestedagainstconventionalloadanddownshot,Figure10.

Figure8–FocusShotLoad

Figure10–BallisticsTest

Figure9–ConcreteFlowerpotTarget

ItwasnotedduringandafterthetestdetonationsthattheconcretetargetsintheFocusShotconfigurationsweremorecompletelybrokenatintersectionoftheperforationtunnels,indicatingthepoweroftheconvergingenergy.

Infigure11theconvergingperforationtunnelscanbetracedinthetesttargetfromthecasingexitpointtotheedgeoftheremainingtarget.

Table1summarizestheresultsofthetests.Allshotswerethroughthetargetsanditwasnotedthataschargeangleincreased,sodidEHD.

Figure11–FocusShot(Converging)TestTarget

Table1–FocusShotTestData

FIELDTESTRESULTS

AfieldtestwassetuptoevaluateconventionalversusFocusShotonaMarcellusprojectinPennsylvania.Thiswasahorizontalwellpadwithtwo~4,050ft.laterals;750ft.spaced;~5,100ft.TVD;drilledinthesamenortheastdirection.Thefracdesign(water,proppant,chemicals)andstagelengthwerecomparablebetweenwells.Eachstagewasperforatedwith5clustersusing3.125in.6spf(12holes)60°phasedperforatinggunswithstandard“goodHole”charges.TheConventionalwellwasperforatedwithconventionalgunsandtheFocusShotwithconverging.Ingeneral,theFocusShotwelltreatedwithlowerpressureandhighersandvolumes.

Figure12comparestwoofthestagesforpressure,rateandproppantconcentration.WiththeFocusShotperforations,thepressurebuild-upindicatestheprobablecreationofasingletransversefracture.Atpumprates>90bpm(barrelsperminute)thepressureremainedconstantasproppantconcentrationswereincreasedwellabovethetargetlevel.TheConventionalwellshowsanerratichigh-pressureresponse,likelyindicatingtheproductionofmultipleand/oraxialfractures.The90bpmtargetpumpratecouldnotbeachievedandproppantconcentrationwaswellshortofthetarget.Inthisstage,proppantdisplacementwascurtailedandfellwellshortofdesign.TheaveragetreatingpressurefortheFocusShotwellwas-6%,or340psilower,Figure13,thantheConventionalwell.

AnX-Y-Zplot,Figure14,comparesallstagesformaximumpressure(Yaxis),sandvolume(Xaxis)andfrictionreducervolume(Zaxis).Mostofthe

FocusShotstagestrendtothelowerrightportionofthegraph(lowertreatingpressuresandhighersandvolumes).ThesetreatmentprofileswouldsuggestthattheFocusShotperforationsweremoreeffectiveintheinitiationofsingletransversefracturesatclusterdepthsandallowedhighersandvolumestopumpatlowerpressures(acharacteristicofidealperforations).

Betterfracturingtreatmentsshouldresultinbetterproduction.Thefirst31daysonthetwowellsshowsapproximately9%betterproductionfromtheFocusShotwell,Figure15.

Figure12–StageFracturingData

Figure13–AverageTreatingPressureperWellandMaximumTreatingPressureperStage

*FRVol.=BubbleSize

Figure14–MaximumPressurevs.SandVolumeandFrictionReducer

SUMMARYANDCONCLUSIONS

Anewperforatingtechniquehasbeendevelopedforhorizontalwellcompletions.Thisperforatingdesignutilizesangledshapedchargeconfigurationstoconvergeperforationtunnelsandenergyatthecenteroftheperforatinggun/cluster.Thistechniqueconvergestheperforatingtunnelsonasingleplaneperpendiculartothecasingaxisatafixeddistancefromthecasingoutsidediameter.Itisproposedthatconvergingperforatingwillbemoreeffectivefortheinitiationoftransversefracturesatthecenteroftheperforationclusters.Ifthenewdesigncanreducethepropensityforperforationstocreateaxialandmultiplefractures,thenmoreeffectivestimulationsandbetterproductionwillresult.

FieldtestresultsindicatethatFocusShotisaneffectivemethodtoperforatehorizontalwellstooptimizefracturingandimproveproduction.FocusShothasthepotentialtoreducetreatingpressuresandincreaseproppantdeliverytothereservoir.Todate,therehavebeenseveralhundredFocusShotstagescompletedinMarcellus,Utica,Woodford,HuntonandEagleFordwellswithoutasingleoccurrenceofascreen-out.

REFERENCES:

1. Behrmann,L.A.,andNolte,K.G.(1998):PerforatingRequirementsforFractureStimulations,SPE39453,presentedatInternationalSymposiumonFormationDamageinLafayette,LA,February18-19,1998.

2. Daneshy,A.A.(1973):AStudyofInclinedHydraulicFractures,SPEJournal,Vol.13,Number2,April1973,pp.61-68.

3. Daneshy,A.A.(2009):Horizontal-WellFracturing:WhyIsItDifferent?,SPEJournal,Vol.1,Number3,September2009,pp.30-35

4. Daneshy,A.A.(2014):FractureInitiationandExtensioninCementedCasedHorizontalWells,HydraulicFracturingJournal,July2014,pp.16-22.

5. Sites,J.(2015):UnitedStatesPatent9,145,763B1,filedMay15,2012,issuedSeptember29,2015

6. vandeKetterij,R.G.,anddePater,C.J.(1997):ImpactofPerforationsonHydraulicFractureTortuosity,SPE56193,presentedatEuropeanFormationDamageConferenceinTheHague,June2-3,1997.

Figure15–31DaysProduction(BOE)

7. Willingham,J.D.,Tan,H.C.andNorman,L.R.(1993):PerforationFrictionPressureofFracturingFluidSlurries,SPE25891,presentedatRockyMountainRegional/LowPermeabilityReservoirsSymposiuminDenver,CO,April12-14,1993.

BIOGRAPHY:

Larry Albert is a BSc graduate of Oklahoma City University. He joined Gearhart Industries in January 1977 as an open-hole field engineer. After Halliburton acquired Gearhart in 1988, he held key management assignments at corporate and field locations around the globe. Prior to leaving Halliburton, he was Senior Director of Wireline Operations. In May 2010, Allied Wireline Services was formed and he served as President and CEO until Allied merged with Horizontal Wireline in 2014. He is currently Vice-Chairman and member of the Board for Allied-Horizontal Wireline Services, one of the largest independent wireline services companies.

Larry has been a member of SPWLA since 1977 and has held officer level positions in chapters around the globe. As a member of SPE since 1984, he has published technical papers and been an active speaker and contributor. He is also a member of API, AADE and AESC.

Gregg Frasure joined Welltec in 2005 as a Field Engineer. He spent 8 years with Welltec holding various positions in operations and sales. Prior to leaving Welltec, Gregg was Account Manager for the GOM helping drive opportunities in the riserless sub-sea intervention market. In 2013, he joined Superior Energy Services in Business Development. In 2014, he joined Horizontal Wireline Services as Sales Manager, after merging with Allied Wireline he became VP of Northern Sales.

Gregg is a member of SPE and has published two technical papers on wireline deployed intervention technologies. He is a graduate of Texas Tech University.

Improved Frac Efficiency Using FocusShot Perforating_HFJ_v8

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