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OilfieldTechnology
February
2014
damageandthetime involved inkillingawellandbringing itbackonline,
savingtheoperatortimeandexpense.Anotherbenefit isthatcoiledtubing
canberunthroughexistingtubing.Notonlydoesthiseliminatethetime
involved inpullingproductiontubing, italsoeliminatestheexpenseof
re‑dressingtheproductionpacker.
Perfectedinmajorshaleplays
CTfirstproved itselfasaviablecompletiontechnology intheFayetteville,
HaynesvilleandEagleFordshaleplays.Here,wherethewellsaredeepand
thepressure ishigh,workoverrigsbecame lessattractiveasacompletions
option. Inaddition,thetransitiontodrilling longer laterals inshaleplays
has ledtotheuseof largerdiametercoil,2 in.and2
⅜
in.tubing.
Coiled tubingpipeof 2 to2
⅜
in. hasbeenprovenhighlyeffective
inhorizontalwell completionswhere it isused todrill out thebridge
plug.Both2 in. and2
⅜
in. pipearebeingused todaydependingon
downholepressure, completionsize, and lateral length.However,
2
⅜
in. diameter is the rockstar inextended reach laterals.Withmore
weighton thebitandbetter control of theBHAoperatorscandrill out
faster, andwith the largerdiameter, higher circulation ratescanbe
achieved, resulting inbetterwellborecleanup.
Likeanywellservicingequipment,therearechallengeswiththe larger
diameter2
⅜
in.pipe.Thebiggestchallenge ismanagingthefatigueof
thepipedueto its largerdiameter–downholepressureandcirculating
pressure,coupledwithpipemovement,canmeanfasterwearingofthe
largerpipe.Asaresult,pipefatigueneedstobecarefullymonitored.
Whenareelofcoiledtubingneedstobereplaced,transportation logistics
andthetimetoaccomplishthetaskcanbecomeacritical logistical
consideration.Theseareall importantreasonsforchoosingaservice
providerwithasolidrecordofCTperformanceandexperiencedpersonnel
thatunderstandhowtobestusethisadvancedequipment.
Thebigquestion:costversustime
CT isoneoftwooptionswhendrillingoutthebridgeplugsusedto isolate
hydraulicfracturingstages inahorizontalorverticalwell.Which isthe
bestsolution?CTorworkoverrigs?Theanswerdependsontheultimate
goal. Isthegoaltosimplyminimisethewellcost?Or is ittogetthewell
onlinefasterandproduction inthepipeasquicklyaspossible? Inplain
economics,wellcostsforperformingtheworkwillbe lesswithworkover
rigs.Forexample, intheEagleFordshaleplay,aworkoverrigcosts
approximatelyUS$7200fora12hrdaywhileacoiledtubingunitcosts
closertoUS$40000/d.But, ifanoperatorneedstogetproduction inthe
pipelinefastandhydrocarbonsonthemarketasquicklyaspossible,CT is
aprovensolutionthatwillhelpthemmeettheiroperationalgoals.When
usedovermultiplewells,theefficiencybenefitsprovidedbycoiledtubing
multiplyaswell,potentiallysavingweeksofvaluabletime.Remember,
explorationmeansnothing ifthere’snoproduction.
ParadigmshiftexpandsuseofCT
WhileshaleplayshavegeneratedgreaterusageofCT,recentparadigm
shiftsregardingmulti‑wellpathsandsimultaneousstimulationor ‘super
fracs’whereagiantmanifold ishookeduptomultiplewellheadsona
singlewellpad,aremakingCTapopularoptionaswell. ‘Super‑fracs’could
continuetorevolutionisedomesticenergydevelopmentbysignificantly
loweringthecostsofunlockingevenmoreanddeeperreservesofshale
gasandtightoilthanwereaccessiblebytraditional fracs.CTcanhelp
operatorsamplifytheiroperatingefficienciesbyeliminatingtheneedto
moveequipmentwhilestillprovidingtimeandspacesavingbenefits,
togetasmanywells intheirdrillingportfoliocompletedandonlineand
hydrocarbonsflowing.CTprovidestheabilitytoquicklymove inandout
oftheholewhenfracturingmultiplezones inasinglewell. Italsoprovides
theabilitytofractureoraccuratelytargetthetreatmentfluidtoensure
completecoverageofthezoneof interest.Aswell,moreuniformtreating
of longtargetzonescanbeachievedwhich isparticularly important
inhorizontalwellbores.Simplyput,CT is importanttoamodern,
technologically-savvywellcompletionsprogramme.
Settofurtherimproveefficiencyinthe
PermianBasin
FollowingtheefficiencygainsbroughtbyCTtotheEagleFordplay
inSouthTexas,coiledtubingnowstandstorepeattheseoperational
improvements inthePermianBasinplay inWestTexas.Traditionally,
workoverrigshavebeentheequipmentofchoice intheregionwith
someoperatorsalsousingCTasanoption.However,withthenumberof
horizontalwells increasing inthearea,thiscouldquicklychange.Consider
thepotential.Whenonetakes intoaccountalltheproducingrock in
theregion,thePermianBasin isthesecond largestfield intheworld. In
fact,there ismoreoil inthePermianthananywhereelse intheworld
persinglegeological formationwiththeexceptionoftheGhawarfield in
SaudiArabia.Now,considerthegeology:thereare4‑7payzones insome
areas.Operatorscouldeasilyhavesixwellsonapadwitheachofthese
wellsgoingafteradifferentpayzone.
AsWestTexasoperatorsfurtheradoptCTtechnologyaspartof
theirunconventionalhorizontalprogrammes,theuseofCT inthe
PermianBasin issteadilygrowing.Fuellingthatchange isexpertisebeing
broughtoverfromengineerswithexperience inunconventionalhorizontal
fields inEastandSouthTexas.The lessons learnedfromtheseareasare
beingsharedwithoperators inWestTexasandappliedtotheareawith
greatresults.Operatorsarealreadystartingtoprovethatgoingafterthese
deeperzonescanyield incredibleresults.Aswellsget longer,deeperand
morecomplex,CTwillbecomeevenmore important intheregion. Inthe
nextthreeyears it isprojectedthatsome60%ofwork inthePermianwill
bedoneusingCTtechnology.
Drivinginnovationtodeliverresults
Coiledtubinghascomea longwaysince itsearlydays intheoilfield.
Changes inthetechnologyhavebeenrapid.Today,CTallowsservice
companiestoget inandoutofmuchdeeperwells,morequicklyand
conductmoreusefulworkthanwaspossibleevenafewyearsago.With
thepercentageofhorizontalwellsgoingupmassively inNorthAmerica
andthosewelltypesrequiringmorecoiledtubing intervention,the
demandforexpertise inCTtechnology isprojectedto increaseaccordingly.
CTwillcontinuetoevolvetohelpmeetthechallengesofthefutureasmore
sophisticatedcompletionsarise intheyearsahead.
Figure1.
AKeyEnergyServicescoiledtubingunit.Thespooled
continuouspipecanreach lengthsofupto48000ftforthesmaller
diameters(1.25 in.)and isusedtoconveytools, log,stimulate,clean-out
andperformother Interventionfunctions inoilandgaswells.
