..

SPE-=utiwSPE 17987

Operation of a Second Steam Stimulation Pilot Project in Kuwaitby K.N. Ahmad and M.M. Milhem, Kuwait Oil Co.SPEMembers

This paper was preparedfor presentationat the SPE Middle East Oil Tachnlcd Conferenceand Sxhlbltion held in Manama,Bahrain, 11-14 March, 1S89.

This paper was aal~Ied for praserdationby an SPE ProgramCommitteefollowin9 reviewof Informationcontained In an Sb8tractaubmlttadby tha author(a).Contentaof the paper,as presented,hava not been reviewadby the Societyot PalroleumEngineersand are subject to correctionby the author(a).Tha material, as presented,doea not neoaaaarilyrefteotany poaltionof the Societyof PetroleumEngineers,itaotficera,or mambere.Paperapresentedat SPEmeetingsare subjectto publicationravlawby EditorialCommttfeeaof tha Soclafyof PetrolaumEnglneera.Permiwlonto copylarestrictedto anabatraotof notmorethan300words.Iliustratkmamaynotbecopied.Theabstractshouldcontainm!aplcuoua aokn@edgrnentof where and by whom the paper is presented.Write PubllcatlonaManager, f3PE,P.0, Box SS3SS6,Richardson,TX 750SS-SS3S.Telax, 7S9989SPEDAL.

ABsTRAcr

1.Mc3pilotsteamstimulationprojectswereinitiatedto studythefeasibilityof applicationof steamforrecoveryof heavyoiloccuringin ashallowdepthreservoirinKuwait.

The first pilot cyclicsteam stimulationprojectwas startedin Septenber1982 with 4wellsl.T%is is stillin the firstproductioncyclewith an overallOSR of 10.316till endSeptember1988.

The secondpilot cyclicsteamstimulationprojectwas commissionedin June1986and steaminjectionto the firstwell conmencedon 25thJune1986.Injectioncentinuedfromwellto welland terminatedin the 4th well on 23rd August1986.

Thesalientfeaturesof thispilotare:

1) Useof treatedbrackishwaterproducedfruna shallowwaterwell.

2) Facilityto switchsteamfromone well toanotherwithoutinterruptionof operationbyusingcombinationsteamandoilheader.

3) Comparedto the firstpilota very shortnaturalflwinglifeof thewells.

4) ~ng distancepumpingof the crude oilwithoutanyadditiveorpipelineheating.

These4 wells are now in the productioncycle and they have produced222,874bbls[341434m3]of oil by 30th September1988withanoveralloilsteamratioof 3.0832.

Therewasno primaryproduction.

Tables& illustrationsat endofpaper.

623

INTRODUCTION

A heavyoil reservoiroccursin Kuwaitat ashallw depth.The API gravityand viscosityofthe oil .raes between12 to 14 API [0.861 to

3 inn?0.9725g/ ] and 600 to 2000 cst ( /s] at7WF [21.1%].

Productionof heavyoil in a placewherehigh quality oil is abundantlyavailablenaturallytakesa lowerpriority.Howeverkeepingthe futurerequirementsin view a modeststarthasbeenmade in Kuwaitto understandheavy oilproductiontechnologyby initiatinga smallpilotprojectin 1982follwedby a similarprojectin1986.

~is paperdescribesthe operationof thesecondpilotsteamstimulationprojectinKuwait.

GEOLWICALANDRESERVOIRCHARACI!ERISTIG

The neavyoildepositsin KuwaitareMiddleMiocenein age and correspondto the evaporites~ence whichoverliestheAsmariLimestoneinIran.Figure1 shws a typicaltypesection.

Reservoirstfatigraphyfromtoptobottomisgenerallyas belw:

Caprockshale.Uppermemberof thereservoir.Lowershalebed separatingtwo membersofthereservoir.Lowermemberof thereservoi~.

l%e lowermemberof the reservoirin thisareaisnonoilbearing.

shalemo~t of theseshalesare not continuousexceptkheonesmentionedabove.

Thesandbodiesin thereservoirare eithershaleor siltstone.The shalesare mainlygreento lightgreencalcareousto verycalcareousinthelowerpartof thereservoir.

The sandand sandstonesare lightbrowntotan in colour,friableto poorlyconsolidated,mediumtowellcalcareousandtightat thetop.

Table1 and 2 givethe reservoirand crudeoilpropertiesrespectively.

PRQJECTDEKIUHION

The projectconsistedof 4 wells,threethermallycompletednew wellsand one old nonthermallycompleteddelineationwell.The threenewwellsweredrilledwitha spacingof 793ft[241.7m].Theareais approximately17 km Southof thefirstpilotarea.

Since there was no utilitiesnear theprojectareaallfacilitieshadtobe plannedandprovidedfor.

Powerwas providalby captiveelectricalgenerator.Fuelanddrinkingwaterwerehauledbyroadtankers.The distancefromnearestutilitycentrebeing160km itposedproblemfromtimetotime,speciallyduringsunmermonthsdue to sandstorms*

The ProjectSiteis 22 km fromthenearestGatheringCentreand the producedoil had to beP- to the@therin9@ntre.A 6-5/8[168mm]OD undergroundline was laid. Considerabledifficultywas experienced@ the initialstagesin pumpingtkw oil whicheasedwith time andexperience.

Othermainequipmentin the projectare atrailer mounted once-throughoilfieldSteamGenerator,a set of WaterDemineralisationandSofteningequipment~andproductionfacilities.

Theprojectusedtreatedbrackishwaterforsteamgeneration.

Figure2 showstheprojectlayout.

SCURCEWATERANDWATERTREATNENT

ihecapacityof theWaterTreatmentSystemis50gpm[0,0032m3/s]oftreatedsoftwater.

The brackishwater is prcducedfrom ashallowdepth water well by an electricalsubmersiblepump to two 400 bbls [63.3m3]eachholdingtank.

Water from the holdingtanks is pumpedthroughan Electrcdialysisreversalsystemtoremovemore than 95% of the dissolvedsolids.Waterrecoverywasapproximately65%.

The Demineralisedwater is held in threenumbersof 500 bbl [79.5 m3] each holdingtanks.l%iswateris thensoftenedthrougha dualtrainsodiumzeolitewatersoftenerand fed tothesteamgenerator.

Table 3 shows the design and acutaloperatingvaluesfor the waterDeminetalisationsystem.

he electrodialysisreversalunitperformedwellduringthesteaminjectioncycleandremovedmorethan99.9%dissolvedsolidswithequivalentreductioninhardness.

Qmunercialgradesodiumsulmite was usedforoxygenscavenging.

Regulartestsforoxygen,pH, hardnessandiron were carriedout usingportablechemicaltestkitstomaintainwaterquality.

Chmnercialgradecommonsaltwas usedforregenerationof the resin.This createdscmeoperationalproblemsdue to the smallgrainsofthesalt.

Attemptsto locatelargegrainrocksaltsnormallyusedforregenerationof resinswerenotsuccessful.

STEM GENEFWIQR

A 1000psig [6,894.76kPa]trailermountedDual fuelonce-throughoilfieldSteamGeneratorwith 25 MN Btu/hr[26.4x 109 J/Hr]capacitywas usedproducing80% steam,usinggas oil asfuel.

SteamGeneratoroperationwas fairlysmoothexceptfor saneminorproblemsin the controlpaneldue to extremeheatin theopendesert.Atemporarycoolingarrangementwith an ordinaryelectricfansolvedtheproblem.

Me steamgeneratorwasoperatedat 550psig[3,792.1kpal to keep the well head injectionpressurebelowtheformatior?partingpressure.

WELLCOMPLETIONS

Out of the four wells,threewellswerethermalcompletionsand one was non thermalcompletion.The non thermalwell was fromoriginaldelineationwells.

Thethermalwellswerecompletedwith7 inch[177.8 mm] N-80 casirrgand had two stagecementationwithclassG cementwith 35% silicaflourand 2% calciumchlorideunder120,000-150,000lbs tension[533,787- 667,233N] andfittedwiththermalwellheads.

The non thermalwell was completedwith7inch 1177.8mm] J-55 casingand cementedwithclassB cementwith 35% silicaflourand 2%calciumchloridewithouttensionand fittedwithnonthermalwellhead.

624

.D17 1 7Q%17 K.Z.N. AHhfAtI 3.U-ru.

AH 4 wellswereperforatedby conventional Thoughtherewas more than 7 monthsgapcasinggunsand had 3.5 inch [88.9mm] OD EUE betweenstoppageof steaminjectionand startofN-80tubing. regularproductionby rod pump,producedfluid

temperatureThreewellsweregravelpackedand one was regularprodu%n~y%d?300F W] hen

triedwithoutgravelpack.Tillend September88thewellhasproduced

Thermal packers were installedin the 57,001bbls [9062.8m3] of oil withan OSR ofthermallycompletedwells.The non thermalwell 2.7143.waswithoutanythermalpacker.

WELLNO.2CX3NBINATIONOILANDS1EANHEADER

Ihewell was gravelpackedand completedA combinationof oil and steamheaderwas witha thermalpackerisolatingthetubingcasing

usedfor injectingsteamandproducingthewells annulus.usingsingleflowlines.

No problemwas encounteredduring steamThis has providedoperationalflexibility injectionand an averagesteaminjectionrateof

and eliminatedworkfordisconnectingsteamline 736 bspd [117m3/dlwas achievedat a wellheadand connectingflowlines.Thishas also reduced pressureof 433psig.[2,985.4kPa]piperequirement.

The well was opened after 28 days ofSimilarlythe well head manifoldswere injectionand 8 daysof soakperiod.It did not

designedfor injectionor productionserviceby flow.Thewellwasswabbedontoproductionanditsimpleswitchingofvalves. sustainednaturalflowfor7 daysonly.

Fig3 showstheheaderandwellheaddetails. Subsequentlya rod pump was installedandthewellwasputon regularproduction.

Thesepracticesreducedmanpowerneed foroperationof thepilot. Tillend SeptemMr88thewellhasproduced

65,311bbls [10,384m3] of oil withan OSR ofThe vrlvesand fittingsare for normal 3.2708.

temperatureservice.For highertemperatureonlypressurederatingwasdone. Duringproductionphasewe facedrepeated

downholestandingvalveprotlemwiththiswell.3-1/2OD [88.9mm] SCH-80pipeswereused

for the combined steam injectionand oilproductionlines.The lines were coveredby WELLNO.3desertsandtoconserveheat.

This well is non thermalcompletion.Thiswasgravelpackedbutcompletedwithouta thermal

OPERATINGEXPERIE~E(INJECTIONANDPRODUCTION) packer.WELLNQ.1

Thoughthewellwasa nonthermalcompletionSimilarto the firstpilotone well (Well no problemwas facedduringsteaminjectionand

No. l)was leftwithoutgravelpackto studyits an injectionrateof 652 bspd [103.7m3/dlatperformanceduring steam injectionand fluid 445psig[3,068.2kPa]wasachieved.production.Thewellwascompletedwitha thermalpacker. Thewellwas openedforproductionafter25

daysof injectionandsoakperiodof 4 days.TheTherewas no problemduringsteaminjection wellflowednaturallyforonly4 days.

andan averagesteaminjectionrateof 837 bspd[133m/dl(waterequivalent)couldbe achieved A rodpumpwas installedandwellwasputonat a WHPof 442psig[3,047.5kPal regularproductiononmfyP. It has produced

42,473 bbls [6,753 of oil till endAfter26 daysof injectionand 6 days of September88withanOSRof 2.7096.

soakperiodthewellwas openedfor production.Thewellproducedby naturalflowfor15daysand WELLNO.4thenstoppedflowing.It was thenswabbedbut itproducedforfurther2 daysonly. lhis well was gravelpackedand completed

witha thermalpackerisolatingthetubingcasingA rodpumpwasinstalledbutafter8 daysof annulus.

productionitsandedUP. Aftera fewunsuccessfulattemptsto cleanthesandandproducethewell Steam injectionrate of 789 bspd [125.5itwasdecidedtoGravelPackthewell. #/d] was achievedat a WHP of 456 psig[3,144

kPa1. No problemwas encounteredduringsteamAccordinglythe wellwas gravelpackedand injection.

regularpumpingproductionwasestablished.

..-

1.

The wellwas openedforproductionafter20daysof injectionand2 daysof soakperiod.Thewelllproducedon NaturalFlowfor 15 daysandthenstopped.

A rod pump was installedand regularproductionccmnencedaftersometime.

rhewell has prcduced58,089bbls [9,235m3] bbls of oil tillend September88withanOSRof 3.7132.

Tbe productionfluidfrom the 4 wellsdidnothaveanymeasurablequantityof gasandcouldbe produceddirectlyto tanks.There was nohydrogensulfidegasproductionalso.

Table4 showsthesummaryof steaminjectionandproductionphaseof the4 wells.

3.

4.

5.

6.

The behaviourof the nongravelpackwell,thoughnot conclusive,indicatesthatsandcontrolmeasuresmaybe neededinthisakea,

HighTDS brackishwatercan be successfullytreatedforsteamproduction.

Long distancepipelinetransportationforheav oil is Wssi;~~ewit~o~-5/8[168mm]OD underground only smallquantitiesat pressuresbelow 2000 psig[13,789.5kPa](limitingsystempressure).

Productionbehaviourof the wells weredifferentfrom the firstpilotwhichhadlong natural flow life, but they arecomparableto any typica4steamstimulationwell.

NONENXATURECRUDEOILTRANXYJRTATION

IWOdifferenttypesof highpressurepumps(dieselenginedrivenscrew pump and triplexplungerpump) wereusedforpumpingtheproducedcrudeto thenearestgatheringcentre.

Theirperformancewas adequatefor thetypeof crudeoil.

Duringthe firstwinterpumpingpresureswere high oftenexceeding2000 psig [13,78!3.5kPal(limitingsystempressure)whenpumpingratehadtobe eitherreducedor stopped.Howeverwithtime the problem easedandnormaloperationcouldbecontinuedduringthesecondwinter.

bblsbspd

dEUEgpmkmODOSRPPMSsTDsWHPW-IT

::

:::::::::::

F$arrels(42USgallon)Barrels of steam per day (Waterllguivalent)DaysExternalupsetendGallons(U.S)perminuteKilometerOutsidediameterOilsteamratio(VOl/vol)PartspermillionSubseaTotaldissolvedsolidsWellheadpressureWellheadtemperature

Howeverhigh volumepumpingpracticablewith this arrangementare in hand to add heatersinstationstosolvethisproblem.

FUTUREPLANS

Additionalwells have been

will not bealone.Plansintermediate

drilledandcompleted to expand the existing pilots.Installationwork has just been completedandplansare in hand to steamstimulatethe newwellsalongwith a secondcyclewith the oldwells.

Once the cyclic steam stimulationiscompleteda singlepatternsteamfloodwillbeconducted.

CIXWLUSIONS

Theoperationof thesecondpilothas shownthefollowing:

1. Moderatelyhigh volumeof steam can beinjectedat lowwellheadpressures.

2. steaminjectioncouldbe done in a simplemannerwithoutmuchmechanicalor downholeproblem.

ST.METRICCOFWERSIQNFACLUtSo~I 141.5/(131,5+ 0~1)CsX x 1.0* E+OOft X 3.048* E-01psigx 6.894757 E+(I)OF (oF - 32)/1.8Btu X 1.05468 E+03

X 2.54* E+O1:1 X 1.589873 E-01lbf X 4.448222 E+OOc@m X 6.309020 E-05

. g/Lm13= ~2/s=m= kpa=Cc=.J=Ilnn. ~3=N= ~3s

* Conversionfactorisexact.

ACKNWLEEGE24ENTS

I thanktheManagementof KuwaitOilCompanyand Ministryof Oil, Kuwait for grantingpermissiontopublishthispaper.

REFERENCE

1. M.M.Milhem& K.N.AhmedPerformanceof aPilotCyclicSteamStimulationKuwait(SPEConfererXe,Bahrain,

Projectin1987).

626

.TABLE1 -RESERVOIRPR(Y?ERTIES

SSdepthko topof sand,feet 300.0[91.4mlGrossoilsandthickness,feet 82.0[25.OmlNetoilsandthickness,feet 45.0[13.7m]Porosity,% 33*OPermeability,Darcy 3.0OilSaturation,% 78.0Pressureat topof sand,psicj 150.0[1034kPa]ReservoirTemperature,oF 85.0[29.40C]

SEE ~79fj~TABLE2 - CRUDEOILPROPERTIES

APIgravitySulfurcontent,wt%Nitrogencontent,wt%Carbonresidue(conradson)wt %Vanadium,ppmNickel, pmVisCositycSt@ 850F[29.40C]

@ 100F[37.80C]@ 2000F[93.30C]@ 300F[148.9%]

12.8[0.9806g/cm3]5.3

1:::71.521.5990.0[mmZ/s]530.0[ml#/s]33.0[m#/s]8.0[mm2/s]

TABLE3 - WATERANALYSIS

CONSITTUENT(AllinPPM)CALCIUMMAGNESIUMSODIUMCHLORIDESULFATEBICARBONATETDSlUTALHARDNESS(asCaCo3)@H

RAW WATERDESIGN ACTUAL

DEMINERALISEDWATERDESIGN ACTUAL

1,146 760364 145

2,343 1,7985,468 3,3811,591 1,350

88 16211,000 7,5964;3657.6

2;5097.7

29

9:185524

3751107.4

289328110602201087.46

TABLE4 - SUMMARYOF STEAMINJECTIONANDPRODUCTIONPHASE

1. STEAMINJFCTIONPHASE

WellNo.

TotalSteamInjectionPeriodCumulativeSteamInjected(WaterEquivalent)AverageInjectionRate

AvarageSteamQuality

AverageWHP

AverageWHT

d

bbls[m3]

%

psig[kPa]OF[w]

SoakTime d

2. PRODWTIONPHASE[Till30thSeptember881

NetOil bbls[m3]

NetWater bbls[m3]

OilSteam Ratio [vol/vol]DaysonN.F. d

1

26

21,000[3,339[

837[133.01

73

442[3,047.5]430[221.1]

6

57,001[9,062

8,354[1,328

2.7143

17

2

28

19,968[3,1751

736[117.0]

74

433[2,985.4]438[225,6]

8

65,311[10,384

6,342[1,008]

3.2708

7

3

25

15,675[2,492]

652[103.7]

75

445[3,068.2]421[216.1]

4

42,473[6,573

3,133[498]

2.7096

4

4

20

15,644[2,487]

789[125.5]

74

456[3,144.0]431[226.1]

2

58089[9,.?35:

5,483[872:

3.7132

15

627

SP _.

y.~.~.~~y--4=&.-.-:.:.-,.,..~...,:~>.

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RESISTIVITY

?

CAP ROCK SHALE

(>

J

MEMBER 2 SAND

(:

Fig. l-Type eaction heavy oil raeewoir in the pilot area.

w. w

RAW WATERTANKS

DEMIN. WATER TANKS

EDR WATERU NITS SOFTNER

//

o-r-----

tI

BURIED TRANSFERL.JNE 65/; O.D

STEAM & OIL IHEADER

5~-..~

..__ ___ ___ __

.-L1J- ---Ii STEAM, GENERATOR

-- . ___

L I1

OIL PUMPS ;

GEN. SET i 1

iB IIGAS OIL ! @TANK ---

p mFRESH WATERTOWER

Fig. 2-Schematic layout of the plant area.

OIL TANKS

5;IIIFIRE HYDRANTS

UNDER GROUNDLINES

_!I

/III1

ISTEAM

51 BLEED LINE *

OIL

iwt 7- T I

!HEADER DETAIL WELL HEAD DETAIL

Fig. 3-Combination oilkteam header and wellhead.