THIS IS A I?RFJ?RZIVT----SUBJECTTO CORRECTION
`
`-
`
`4
`
`A CONTINUOUS
`
`MULTISTAGE
`
`FRACING’
`
`TECH-N IQUE
`
`By
`
`1
`
`K. R. Veb3ter,Asso+ate Memb’~rA1~~ v- c“ ~ine~ Jro~and SS C- ‘er%
`onahans,Tex.
`MembersAIME, Gulf Oil Corp.,Houst~
`
`~ication
`
`Rights Reserved
`
`~~
`
`.,
`
`Downloaded from http://onepetro.org/JPT/article-pdf/17/06/619/2218279/spe-977-pa.pdf/1 by Robert Durham on 05 September 2023
`
`This paper is to be presentedat the ggth Annual Fall Meetingto be held in Ho@on, Tex., on
`Oct. ll-llj 1964, and is consideredthe propertyof the Societyof PetroleumEngineers. PermissionGO
`publishis hereby restrictedto an abstractof hot more than 500 wor%. with no il.lust~>tions,unle~s i
`the paper is specifically’releasedto the press by theEditorof’the Journalof PetroleL:,Technologyor
`the ExecutiveSecretary. Such abstractshouldcontainconspi.cuous,acknowledgmentof where tid by whom
`the paper is presented. publicationelsewhereafter publicationtn Journalof PetroleumTechnologyor
`~Journal
`is grantedon request,providingproper creditis given that
`~~~
`publicationJnd the originalpresentationof the paper.
`
`Discussion cf this paperi.sinvited. Three ctipiesof any discussionshouldbe sent %CIthe Society
`of PetroleumEngineersoffice. ‘Suchdiscussionmay be presentedat the above meetingand considered
`—
`fQr publicationin one of the two SPE magazineswith the paper.
`
`,
`
`ABSTRACT
`
`Wells with multipleproducingzones can be
`fracturedone zone at a time during-continuous
`pumpingwith a high degreeof probability~of
`treatingall zonesby [I] perforatingwith
`chargesClesigne&to produceround,
`lxm’-f=
`[21perforatingthe s~e low n~ber of
`holes;
`holes [usuallyeight] into each zonej [3] perfo-
`rating in acid; and [4] using scale?balls be-
`tween frac stagesexactlymatchingin number the
`holes in each zone.
`
`determinethe holes requiredper zone based on
`flow rates sri total cross sectionalarea of the
`perforations.
`
`Redioardve ?rac sand end gamma ray trac-r
`surveyaha<e been used in conjunctionwith strad.
`dle packersto determihethe zones treated. Sue,
`cess r.atLoscalculatedas the number of zones
`fractureddividedby the numberof fractures
`attemptedhave been found quite high in 7-8 zone
`wells and still greater in wells with fewer
`zones.
`
`During field trialsof the process,recov-
`ered flu~d-cutsealerballs;tndicatedthat quite
`oTten jet perforatedholes had poor roundnessand
`raggedburrs preventinggood seed.. It was neces-
`sary to have Jet chargesand guns redesignedto
`provide consistentlyround sad !nzrr-freeentrance
`holes. Perforatingthe same number of holes per
`zons eliziinatest~e guessworkwhen detern.ining
`the number of ball sealersto use ‘perstage.
`,
`Experiencehas shownthat perforatingin acid
`reducesbreakdownpressures,allowingthe”pro-
`cess to be used in areapwhere previousfracing
`indica%edthe.methodcouldnot be applied. UsLng
`sufficientholes per zone to handle the total
`.pwuping.rateat-.alQw..differenti&.pxessWe_pre-
`vents breakingdown more than one zone at a’time.
`High differea%ialpres~me.from too f’ewholes
`consumesenergy and adds to the cost of the
`treatmenk. A calculationprocedureis used to
`
`Referencesand illustrationsat end of paper.
`
`The method is less expensivethan treating
`one zone ata time using isolatingpackersand
`is much surer of producingmultLplefractures
`than simultaneouslyfracinggenerously
`perforate
`multiplezones. Continuousmultistagefracturin
`producesmaximumfract~e area for a given injec
`Won rate as comparedwith simm..ltaneousinjectio
`into multiplezones. The m@.ti.stagetechnique
`also allowsuse of all the steps consideredesse
`tial to good, sing~e-stagetreating.
`
`Results-offield trialshave consistently
`indicatedverticalfractures. The fracture
`orientationhas been evidencedby low treating
`pressure.gradients.aad.by gaima ray.tnacer.sur.
`veys.
`
`Field work tith radioactiveproppingagents
`provideda means of checkingthe qualityof the
`cementjob after fracturing. What had been
`
`IWS EXHIBIT 1052
`
`EX_1052_001
`
`

`

`A CONTIliUOUSMUL2?&CA(3EFRACIN(3TECHNIQUE
`
`‘
`
`.
`
`.,
`
`Sp’E!-977
`
`Downloaded from http://onepetro.org/JPT/article-pdf/17/06/619/2218279/spe-977-pa.pdf/1 by Robert Durham on 05 September 2023
`
`considereda satisfactoryprimary cementingtechn-
`ique was.found Zn many cases after fracingto
`give channeledcementfor considerabledistance”
`above the pay sectionand showedpoor separation
`or no separationbetween zones. The cementpro-
`grsm in one fieldwas modifiedand f5.nally
`,included:
`
`1. Reciprocationduring cementd.ngof the
`pipe until the top plug bumped.
`2. !rwOplugs.
`3.
`Centralizersand Scratchersacrossthe”
`i,
`pay..
`4.’ Sixteenper cent’gel-saltfill.cement.
`with regularheat to cover the pay section.
`5.
`Turbulentflow of the fill cement.
`
`‘ Wtth this procedurenear~yall of the treat-
`ments have been confinedto the pay sectionarid
`‘theseparationbetween zones is greatlyimproved.
`Data were determinedindicatingthe spacing
`“requiredbetween sets of’perf’oratLonsto prevent
`communicationduring fracing.
`
`FPoductiondata kre presentedshowingthe
`.improvetiebtobtainedwith controlledfrac %reat-
`rnents.
`
`The generaltechniquehas also been applied
`to acidizationof multiplezones.
`
`INTRODUCTION
`
`.’
`Fracturingof mu.ltizonewells becomesvery
`expensiveand even prohibitivelys? in some wells
`#f each zone is separately%reatedwi.thmechani-
`cal devicessuch as bridgingplugs and packers.
`Separatetreatingof this type requiresextra
`rental of tools, additionalrig time, and repeat-
`ed chargesfor the frac trucks.
`.
`
`,Amethod commonly known as pinpoin%~or
`limitedentry fracturing will providepositive
`simultaneousmultizonetreatinglbut it disadvan-
`tageouslydividesthe injectionrate among the
`zonesbeirigfrhctured,resultingin low injection
`rates per fractureand thereforelimitingfrad-’
`ture extension. The meth,odis also dependent
`upon high injectionpressureand’thusre@.res a
`large amount of pump horsepower. Other methods
`using variousforms of gels and temporaryblock-
`inghaterLa3s have been bried but they offer poor
`controlof fractureplacement.
`
`flow meter surveysand radioactivetracer surveyE
`used to checkthe effectl~,messof this guess-
`work approachshows that it resultsin large’num-
`bers of.uqfracturedzones.
`
`If multistage%reatingwith ball sealersis
`to reduce corapletiontime and ~ost it must ensure
`that all zones are t+??eated.In’addition,such
`%reatingmust.allow sufflci~~tflexibilityto
`permit followingthe requirementsof designed
`fluid treatments.
`
`8
`The generalizedrequisitesfor effective
`fracturingye consideredto be as follows;
`
`1. TreatmentQf all zoneb in which stimu-
`is desirable,using sufficientvolumeto
`Lation
`give opttiumeconomicfracture‘extension.
`2. Corxecttype and concentraliionof pro -
`~1
`ping agent ho producehigh capacityfractures.z
`3.
`ETfectiveproppingagent placement
`xequirlng~pearhea~,proppingagent fluid,ar$nc
`overflush.
`4. Yluid loss contro15Ln spearhead”a~d
`proppingfluids and viscositycontrolin spear-
`head~ proppingfluL& and flush.
`
`In order to meet these requirementswith th<
`least horsepowerit is essentialthat the frac
`flui& enter one zone at a time. This will reduce
`-thechancesof a,screenouttid provide’the
`-
`grea%estdepth of penetrationat a-givenpump
`rate.
`
`The purpose of the mu.ltizopefracturing
`method $escribedherein Is to incorporate+nto a
`continuousoperationall the requirementsher&-
`tofore possibleonly in repeatedsingle stage
`frac jobs. ,Inmost cases o! this type, $rea’t-
`rnentcan be conducteddown the casingat high in.
`jectionrates withoutlarge prea’surelossesdue
`to friction>b~t also can be appltedthroughthe
`tubing if necessary. The method algo applies
`directlyto multlzoneacid Jobs; It,hasbeen
`repeatedlysuccessfulin the CraneyMonahansj
`Victoria>‘OklahomaCity and Hobbs”areasof Gulf.
`Initialef$ortswere made at Crane by the local
`personnel,but most of the supportingdata here-
`in were developedat Monahans.
`
`G!WWWLMETHOD
`
`In brief, the method consistsof the fol-
`lowings
`
`Fracturingseveralzones in a well-byuse of
`‘ball sealersto divertthe frac fluid to a new
`zone is unreliableas usuallypracticed. One
`reason Is the difficultyin determininghow many
`_b_a_~_sealersto inject. When.thewell has thick
`and thin Bones,with a correspondingvariationiri
`the number of perforations,it is impossibleto
`detemninewhich zone treats first so that the
`correspondingnumber“ofball sealerscan be in-
`jected. This processbecomesmore complicatedas
`the number of zones increases. Straddletools,
`
`1; Petioratein acid each zone to be st3mw
`lated>using the same small,number of holes of
`crcks sectionalarea-sothat
`sui’ficfenttotal
`pressuredrop.at.thedesignpwqp rate will be lo~
`“erio-izfi-[abo”ut”150’;pslj--to-””a70-id--siinUteuieouso
`‘“
`bre~down of anoth~rzone.
`‘
`2. Use a perforatingdev%cewhich pr~duces
`rouhd,b,urr+reeholes of laIOWIIsize.
`3.
`Based cmthe most permetiblezones,desi~
`a fluid
`stage consistingof spearhead,prop-
`
`IWS EXHIBIT 1052
`
`EX_1052_002
`
`

`

`;U-
`
`m.
`
`n.
`
`WXILUJAL!IA>.
`
`w .
`
`U*
`
`WAAW.1*
`
`VAX.
`
`mu
`
`w.
`
`u.
`
`JJ X1.u,
`
`L
`
`Downloaded from http://onepetro.org/JPT/article-pdf/17/06/619/2218279/spe-977-pa.pdf/1 by Robert Durham on 05 September 2023
`
`will be fired. Hole diametermay vary consider-
`carryingfluid,and prop agent as for a single
`ably with clearance.6 The servicecompanies
`zone frac job. Ef an acid Job$ design an appro-
`usuallyreportthe hole size at 1/2 in. clear-
`priate fluid stage for the zoae.
`ance$ but they seldomprovLdea means of contXol-
`4. Pump the first spearheadand propping
`ling or firing:thejet chargesat *his clearance.
`fluid stage as designed}followedimmediatelyby
`the number of sealerballs matchingthe number of
`Nearlyall wells have enough deviationto cause
`the perforatinggun to be againstthe casirig,’
`h~les in one zone.
`stmilarto the postkionshown in Fig..2, This is
`5.
`Repeatthe fourth step for each stage
`an exampleof a 1-11/16 in. capsulegun with 90°
`except that sealerballs shouldnot follo!wthe
`,,
`phasing inside7 in. OD 20 lb casing. Two,ofthe
`@et stage.
`[BandD] will strikethe casingat
`jet streams
`the last
`6. Pump in flush fluid following
`an angle and ~roduceelongatedholes wit+huneven
`‘stage. Underflushfor a frac ,job,overflushfor
`burrs wh.tchball sealerswill’notseal. Clear-
`an acid job.
`f,
`ante for one.ofthe Jets [A] is so great it may,
`not producea hole; the other jet [c] will _p$o-
`The use’of some radioactiveprQp agent with
`duce a.holeat zero clearancewith less diameter
`the usual prop materialhas been of great aid in
`than normallyreported. Althoughthis is an
`developingrules for spacingthe fracturesand in
`determiningwhen cement ~ob.eallow channeling”of extremeexample,it demonstratesthe importance
`of controllingclearancehd positioningthe
`the frac fluids.
`charge so that it will be”flrednormalto the
`The full significanceof the above procedure casing. This cap be accomplishedby several
`methods. A magneticpositioningtool or a mechan
`is not immediatelyapparent,and the following
`Ical decentralizingdevice can be used and all
`items are presentedto explainthe methoa and
`the chargesfired in a vertical~ine in the same
`illustrateresults.
`direction. Mother method is centralizingregu-
`lar carrierguns. A carriergun of near casing
`diaineteraoes a fair job. But in any event,the
`perfomnancecurve or API RP-k> tests shouldbe-.
`obtainedfrom the perforatingcompanyand evalu-
`ated in terms of possibleclearancevariationsin
`the well,to ensurethat hole diametersare ap-
`proximatelycorrec%.
`
`PERFORATING
`
`n order to assure treatmentof each and
`.eve,ryzone in a multiz~neattempt,perforating
`must be controlledin a specificmanner. If it
`were possibleto-perforateeach zone with one
`h~le large eniughto acceptthe pumpirfgrate and
`.
`then drop one ball sealerof the correct
`size,
`this would seal the hole acceptingthe fluicl.
`In additionto roundnessand size requ,ire-
`ments, pexforatlonsshouldbe,burr+freefor
`hing
`pressurewould thenbe increasedto the
`efficient$ealerball seating. @is is evident’
`value necessaryto break down the next zone.
`from the sketchof a typicallarge hole perfora-
`T@s is PO? practica13but it is possibleto p;r-
`tton shown in Fir 3 and confirmedby recovered
`.forateeach zone with eno~h holes-topermit pas-
`fluid-cutsealer .J21s. To date two service
`sage of the fluid with a low pressuredrop) and
`companieshave respondedwith field equipmen%to
`bymatch~ng the number of sealerballs with the
`requestsfor burr-freejet perforatingdevices
`number of holes in e~ch zone}the same effect can
`be accomplished. The most commonnumber of holes meetingall the requirements. tith tools de~elo~
`holes slightlylargerthan 0,6 In. ad-are decen-
`per zone is eight,but the numberto be used $% a
`calculatedquantityas illustratedbelow..
`tralizecicarriergums fi”?~ngas many as four
`shots per ft.in one direction,
`One develo>sa
`slightridge on some holes but 1s quite satis-
`factory;,the other has well roundedshoulders.
`also shown in Fig,
`Typical
`holes
`from these.,are
`3.
`Sketchesratherthan photographsare used foz
`clarityin reproduction.
`
`10 Choosea perforationfrictionpressure.
`A small differentialpressureor perforation
`frictionis necessaryto sea% ball sealers;
`100-
`200 psi is usuallysufficient.
`2. Ik?terminethe,flowrate per ~erforation
`that will produce’100-200psi differential. This
`may be calculatedor tskeu from a curve such’as
`Fig, 1. Nextp dividethe individualperforation
`flow rate into”the”total pump rate to obtain the
`number of holes requiresfor each zone.
`
`PerforatingIn acid %s a step thet experi.enc
`in both carbonateand sandstonereservoirshas
`provennecessaryif alJ.zones are to break down
`within the Zimitingpressureof the casingor
`“tubing.” The servicecompaniesao not objectto
`perforatingin acid if
`a few precautionsare fol-
`In general,the fewer the number of holes
`lowed. The acid shouldbe well.inhibitedand
`.used,the less chanceof leakageduring fracing.
`used tio adequatelycover the interval.
`This favorsrelativelyMrge dismeterperfora-
`eno~
`—...
`—...
`As G exaiipl.e,for-25-bAmj-”150-”psi-di?~‘- The-rernaind@r”of ”the”hole-shotitbe-loadeh-ti”th-’”a
`tlons.
`clean fluidwhich will wash the wirelineantiper-
`ferential,and 0.6 in.’dismeterholes, 10 holes
`.are required.
`mit correlationfor aepth controAabove the acid.
`Correctlyspottingacid’undermore dense salt
`wateris difficultand ‘theJob Is surer if the
`water is li@tened or the acid weighteawith salt
`:,
`
`It is necessary‘tokncwthe eutrancehole .
`di~eter producedat the clearancethe charge
`*
`
`—.
`
`—.
`
`..-- ..—
`,:-.-
`
`IWS EXHIBIT 1052
`
`EX_1052_003
`
`

`

`A CONTZNUOW MUI/l!IS!I
`
`Downloaded from http://onepetro.org/JPT/article-pdf/17/06/619/2218279/spe-977-pa.pdf/1 by Robert Durham on 05 September 2023
`
`mrmmGzoms
`
`Definingi zone for FracturingpurposesIs
`usuallydone from logs and is a simple,operation
`when the ‘producing”formationsorzones are con-
`‘ siderablydifferentfrom ,theformationsseparat-
`ing them, such as when cl,eansands are separated
`by shales: Howeverjdefininga zone is much more
`difficultwhere porous zones containsharp varia-
`tions in porosityover short intervals. In for-
`mations of this type it is necessary
`to
`estimate
`the height of vert~calf’ractures,inorder to,
`d&temz%nethe number of entriesrequiredto &reWl
`all of’thepa~ section. The fracturesap~earlx)
`extend in generalto the limit of an intervalOP
`varied porosityand this”thendefinesa zone of
`porosity. However,if the %vne of porosityis .
`thick),the fracturewill not ’”appearto extend
`across the whole zone. Entriesare then spaced
`about 50 f% apart.
`,,
`
`There must,be sufficientdense formation
`between zones to prevent,$hefracturefrom
`extendingacross the dense’fr+ma%ionand %0 pro-
`vide a good cement seal. A “rule~f thumb” used
`by a number of engineersfor this ~istanceis
`25 ft.
`Low porosityintervalsof five or 10 ft
`seldomprovide sufficientseparationbetween
`zones to be fractured.” Fig. 5 shows communica-
`tion between sets of $erforakionsat different
`spacingas found after fracturingin one field.
`the method of determinationWas based on the
`spread o.fradioactivesand between sets of per-
`forations. As an ill~tration, the gamma ray-
`neuiron log from a Devonieawell is shown as Fig,
`6.
`I%&as four zones@ndwou.ldrequirefive
`entries. Suggestedpoints of entry have been
`marked on the log.
`
`“.._
`While ~he”remaybe some objectionto not
`perfora@ng aporoue intervalimmediatelyad~a-
`to anotherselectedfor perfora~%ngjexperi-
`cent
`ence indicatesgood wells ‘areproducedand radio.
`active tracer techniquesindlca’tethat ve~i.cal
`fracturespass %h~ygh both intervals. In any
`event? the overallmethodidescxibedcertainly
`producesbetter spaced st$mulatlonLn thewell.
`,tha is possiblewith saturationof all porosity
`with perforations. Saturationperforating
`respltsin holes in all desiredIntervalsabut
`and large
`control-offrac placement
`is
`losf
`uusttiulatedintervalsresult.
`
`,’
`“orCa C12. When thi~ is not done, perforating
`must be accomplishedquicklybefore the acid lu-
`bricatesout of the intervalto be perforated.,
`
`It is possibleto use horizoktklplane per-
`foratingfor the method. If the shallowestzone
`treats first and’$sblankedoff by the first
`stage of ball sealers,all the remainingstages
`and sdalersmust.pass throughthe restriction
`made by $he seatedballs, In small M.ze casing
`it maybe difficultfor%he balls to pass through
`the restri,ctlonwithout colliding. However,the
`method is feasibleand is actuallybeing used
`where sufficientclearanceis available.
`/
`
`BALL Wwms
`
`Rubber coatednylon [RCN]ball sealersare “
`recommendedin preferenceto solid rubberballs.
`The etrengthof solid rubberballs is greatly
`decreasedwith small rises in ‘temperatureand
`the balls may fail by shear or by deformingand
`squeezingthroughthe holes. !l?hisconditionwas
`experiencedon a well when a few solid rubber ‘
`balls were mixed with RCN balls. ‘I’heywere
`found to have deformedalmodt sufficientto pass
`throughthe perforations. However,rubberballs
`have been used successfullyi.nlow temperature
`wells.
`,
`
`Jet chargesfired a% the stie clearancewill
`produ e entranceholes with some variakionin
`size.z Some servicecompaniesplot the clear-
`band ratherthan
`ante vs. hole size curveas
`a line of the ayer,agehole.,,zes. The baud will.
`&
`includethe m&xim& and minim
`hole sizes ex-
`pected. When choosing.thesizeof ball sealers
`!-itis importantto know the maximum size hole
`@#d&@ selectball sealersaccordingly. 2roubie
`is av&kxledif the nylon cores are slightlyIargez
`t~an the”hole.,.
`,,
`
`A valuablecheck on the performanceof both”
`the sealerballx+’andthe perforatingdevice is
`the inspectionof:sealerballefollowingthe job.
`Each ball shouldbe found to be imprintedwith
`the perforationshape. They shouldshow round
`impressionsof correctdiameterand giveno
`evidenceof having washed out or le,aked.This
`checkmay.indi.catenecessarychangesin the
`perforatingdevice or ball sealers.
`
`Fig. 4 shows a fluid-cutsealerball .kypical
`of many obtainedfrom jobs using conventional
`For an unfracturedwell.to developmaximum
`producingability}most of the permeableinterval
`perforations,withburrs. While the leakagepro-
`duced by a few of thesetill not seriousl.yaffect
`shouldbe perforated. If ?well.is to be.pro-
`duced throughhigh capacl:yfractures,these w
`a job, more than a fey will thief enough fluid tc
`be eeta6Ushed adequatelythrougha llmitednum-
`preventbreakdownor rendex,ineffectivetreatment
`ber of-perforationsas’describedabove. .Entry.ix
`of the.lastzones. ,Alsoshowz.arenon-fhxid.cut.
`.......-..— ——— ..-.—------
`‘:%he-@p6~~art of the reservoirshouldbe used ix
`balls from burr-freeholes. The balls f%”b”iiik-
`free holes often have a ring of impregnatedsand
`water drive zones and in the lower part of’the
`grainsupon recovery>as shm.on the secondbalJ
`reservoirin gas cap areas. A midpointshouldb<
`used if’both gas and wqter problemsare expected,
`from a burr-freehole.
`
`—
`
`. ..
`.-.
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`“
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`-.,
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`-
`
`IWS EXHIBIT 1052
`
`EX_1052_004
`
`

`

`t
`&977 #
`
`“
`
`K. R. WEBSEER,W. C. (3
`
`B, JR. and S. C. BERRY
`
`.,
`
`G
`
`,/,.
`
`Downloaded from http://onepetro.org/JPT/article-pdf/17/06/619/2218279/spe-977-pa.pdf/1 by Robert Durham on 05 September 2023
`
`2. Underflushto preventflushingthe R4
`material‘toofar ~rom the weXl bore for detec-
`tion. :
`Circulate
`3.
`the hole to remove sus$ended
`fine radioactive‘particlesand remove fill UPC
`4. @g at the same speed,time const~t ant
`sensitivityas the originalor base lQg, A Pepeat
`log under these same condLtLonswi~ verifythat
`the tools are functioningproperlyanfithat the
`hole is free o)’‘suspendeclfine RA particles.
`
`A radioactive+nacer,canbe changedby+.log-
`ging speed. A speed of20 fpm is prefez’redfor
`bpth “theorfgitialand tracd~ surveys. A scintil.
`lation counteris preferrefi%oless sensittve
`through-tubingGeiger countertools.
`.,
`Tracer surveysand”;adioactiveprop are -
`recommendedfor at least a few wells within a.
`field to obliainabetter pictureof the treating
`pattern. After the patternis ‘establishefi,t~e
`cost may not be just%?iedfor all wells. How-
`ever, the cost Cou-,ti$e greatlyreducedby k–m-
`nLng the radioactiveproppingmaterialincthe
`frac ~ob,andlogging only when the well does not
`respond.properly. The’techniquecap be extremex
`valuablein determiningthe neefi and’directiono:
`workoverattemptswhen It indicateschannelingt(
`htgher or lower intervalscontaininggas or
`L,.
`water.
`
`,“
`
`PRIMARYCEMENTING
`
`A~soundprimary cementjob is criticalin
`well completion.andstimulation. If the cement
`doe? not provide.Lsolationbetween sets of per-
`forations,oriezone will fractureinitiallyin .
`multistage attemptsexxi,subsequentstageswill
`feed through clpzmeledcement into the sewe frac
`ture. ,Or worse, a fracturewill occur at some
`undewiredzone well outsidethe intervalselecte
`for treatment. In some instancesabnormalgas o
`water productionmay indicatesthis confiition;
`but more often the productionresultsare”poorj
`and”ilueto the many Uncertaintiesinvolvecizare
`unrecognizedas such. @Lthese points were
`clearlyillustratedin multistagefracturingin
`the North WartlEstes Field at Monahans,l?ex.
`
`The three densitylogs shown on the Iefi of
`Fig. 8were obtainedfrom three wells fiuring
`early attemptsat continuousmultistagefrac-
`turing+ On these Iogtiis incticatedthe extento
`travel~ofradioactivesand which was obtainedin
`the manner describedin referenceto F}$: 7.
`Th
`frac ,f+uidand prop ‘arechowito hav~’%raveledal
`much as 150-200ft above the Queen sahd Snfiall
`s@s o? perforationsconmnmi~ated,:indicatingfel
`$$_~T?~ac+~s_oeg~re_d,_ln th+~g%yl ~~?grou
`of 14 wells, six had very S-k’ilarresults.
`‘“
`This
`aleazlyshowedthat the multistageattemptswere
`failingdue.to inafiequateprimary cementing.
`
`Prima@ cementingpracticewas alteredand
`the finalprocedureincluded:
`
`-,-
`
`....-=.+....-...
`
`..... .. ......
`
`RADIOACTIVEPROP AGENTSAND TRACER SURVEYS
`
`Extensiveuse has been made of radioactive
`proppingagents and tracer surveys. These pro-
`vi,deinformation’indicativeof the following:
`
`1.’ Whetherall z?nes sele”cted,weretreated.
`2. Ver%icalor horizontally-oriented
`fractures.
`‘3. Extefitor height of verticalfractures.
`.4. Cormaunicationbetweenperforations”orto
`undesir~dzones.~
`..’
`
`from vertical
`Channelingwill often
`differ
`fractures&n that the increasedradioactivity
`will only go one &irectLonfrom the point of
`entry. A short set of perforationswill usually
`be placedwithin the boundariesof a porous in-
`terval, in which case a verticalfracturewould
`produce increasedradioactivityboth above and
`below, as shown,inFig. 7.
`However,when One or
`more sets of perforationsare connectedby radio-
`activity,the method 1s not capableof clear~
`distinguishingbetween chanrieltngthrough.the
`amul.usCT verticalfracturing. Fig. St there-
`f’orejcan only be interpretedas indicatbw the
`conmunl’cationbetween sets of perforations
`resultingpossiblyfrom the combinedeff@ctsof
`both types of conznunicatlon.Logs showingtwo ox
`more sets of.perforationsconnected can only-be
`positivelyinterpretedas-indicatinga minimum o~
`one fractureand a possiblemaximum pumber of
`fracturesequal to the sets of perforationscon-
`nected. Straddlepackertes%s in a number of
`%ellshave shown that communicationdoes exist
`when indicatetlby radioactivity.
`
`The gamma ray tracex log is a.continuous
`recordingof the measuredcount rate of gemma
`radiationacross ari,iziterval”ofa well. The
`count rate”i.saffectedby [I.]the strengthof th(
`source; [2] dist=ce from sowc@ of the d@te~tQr,
`[3] the”mount or shielding. Shieldingis pro-
`porlxtonalto the densi%yantithicknessof the
`materialbetweenthe source~d the detector.
`-Radiationat the strengthUs’efiin fracture$reat,
`ments can only be’detectedfor a short distance
`of about one foot in fluid =d even less when
`shieldedby casingjcementand foimation. For
`this reasontlieradioactivityin a zone sho~d..
`not be interpretedin tenus of the quantityof’
`frac fluid injectednor taken as ameasure of th(
`depth of fracturepenetration. Hoi?everjit’is O’
`interestthat t@ough a fracturecizon=ethe rtiio
`activitytends to increasewith porositytindi-
`cating po8siblythat more prop agent is retained
`inhighqr porositystreaks.
`
`1. Use raai.oac~ivema’teria.lthroughoutthe
`entirefracturetreatment”ata concentratioriof”
`than 1 mc of’iridium192 per 1$000 lbs
`no less
`of sand or 0,2 m.cZr.Nl.g5per 100C?lbs of sand.
`
`. ...
`
`IWS EXHIBIT 1052
`
`EX_1052_005
`
`

`

`1, Centralizersat about 30 f% ’spacing.
`2. Two cementingplugs.
`3. ~Reciprocationduring cementinguntil the
`top plugs seated.
`4. Avolume of flush cement(aonsLs\iugof
`.
`16 per cent gel cementwith 0.2 per cent retarder
`~nixedinto water with 2 per cent predissolved i
`.),,
`sodiomchloride.7
`5. Neat cementacross the pay.
`6, Scratchersacross’thepay at 10 ft
`spacing.
`,.
`
`Item 4 provtdedan economicalflu$h vo~ume
`cementwith exceptionalflow properties,allow-:
`ing easy establishmentof ‘turbulentflow. Prac-
`-kj.ceat the the the first three logs in Fig. 8
`were obtaineddid not includeRem 6, and r6cip-
`rotationwas done onlyuutil the cementreached
`the bottom of the casing.
`
`~.-
`
`-,,
`
`58to 95 per cent of those e.ttempted.Again,the
`reasbn for the undeterminednumber of fractured
`zones rangingfrom 14 to 23 is du’eto’several
`zones being spannedby i.ncreaBedradioactivity.
`
`If the same fractureshad’beeuattemptedone
`zone at a time> with bridgeplugs end packers.to
`‘isolate%he pkrforbtions,th~ same difficultyIn
`$leterminingthe”numberof fracturedzoneswQuld
`hwe existed. In other”wordsjthe possiblelow
`ratio above is a resultof decisionson perfora-
`tion spacingrather than a fault of the method.
`Where zones are separatedby 45 ft or more there
`2’sreason,to,believe,%hat100 p,ercent of the
`zoneswould be consistentlyfracturedby the
`method presented,assuminggood cementJobs and
`no extreme,unusual circumstances.
`.’.
`
`The final measuieof any treal+ngprocessis
`the oil produced>but productiondata on enough
`“ i!hethree densitylogs on the right in lllg. wells to give reliablecomparisonsi? difficult
`8 show.thedramaticresultsLnthree,owellstypi,- to obtain. @rge numbersofwel.lsIn the North
`cal of almostall logs from a large nuil%erof
`War& Estes Field have been fracturedin the Queen
`subsequentwells. Frac s<zndtravel outsidethe
`band during the past year. All these were
`attempts,atimultistagefracturing,but the wel,l.s’
`Queen sand,waseliminatedand there was separa-
`t%on betweenmost sets of perforationsindicating cornple~edduring the last six months have been
`intensivelystudiedwith the view of’moreeffec-
`multiplefr~ctureswere produced.
`tively controllingthe frac placement. The study
`qutcklyindicatedthe need for improvementin
`cementing,and the changesdescribedwere”made.
`Improvementin perforatingin ac.tdhelped’hold
`breakdownpressuresto within pipe strength
`limitsand burr-freeperforationsstopped~sealer
`ball leakage. These Improvementsshowedfewer
`missed zones and sho,uldbe reflectedin increased
`prod~ct.ion,
`
`Downloaded from http://onepetro.org/JPT/article-pdf/17/06/619/2218279/spe-977-pa.pdf/1 by Robert Durham on 05 September 2023
`
`The by-passingconditionwould have gone
`unrecognizedand uncorrectedwithoutthe use of
`radioactivesandand tracer techniques;end the
`multistagefracturingprocedurewould have
`v
`appearedto be much less succe$sfql.
`. .
`
`RESULTS
`
`Probablythe most essentialmeasure of suc-
`The production’?romten recentlycompleted.
`cess for a conthuous multistagetechn+queis the
`offsets
`wells has been comparedwith 17 on strikq
`per cent of the zones attemptedthat are frac-
`t.ured.The.bestindicationsavailable.in quantt- completedprior ‘bothe changesdescr,ibecl~Com-
`parisouof the~initialpotewbialtests skiowsthe’
`ty are the radioactivetracer surveys;but as
`new wells have g 3.5-foldincreaseover the off-
`statedpreviously>when more,thanone set of per-
`sets. Water productionis less by 25 per cent
`f’orationsare spannedby a single Intervalof
`and the &ecreaseis probablydue to confiningth,e
`increasedradioactivikyt,thereis no sure deter-
`fracturesto the &esiredformation.
`mi.nationof the riumberof zones fractured. The
`i’
`number could vary from one to as many as the nwz-
`ber of sets of perforationsspannett.Fig~ 5
`This methoclof multistagetreatinghas been:
`used successfullyin a “number.of other reservoirs
`clearlyindicatesthat by arbitrarilyincreasing
`the spacingbetween sets of perforat~onssthe
`in the PsrmianBasinj and especiallynear Crane,
`where the basic method was first tried several
`number.ofunspnned sets.would decreaseand the
`years ago. It”has also been uses in the Darst ‘
`would be more clearly
`number of zones frticturecl
`Creek,Como, aua Pittsburgfielas”ofTexas} aucl”
`defined, However,this is at the cost of omit:
`severalother fields in Oklahoma. The same prin-
`king attemptsto fracturesome of the porous
`cipleshave been successfullyused in multistage
`intervalB. In the wells studiedthe nwber of
`acidizing.‘Howeverjthese scaliteredtreatmenlis
`sets of perforationswere o$ten reduced [spacing
`increased]on the premisethat radioactivity
`&i& not provide the direct comparisonof a large
`from one..setwould indicatea verticalfracture . ‘nwuberof we~s in a singlereservoiras observed
`in the North W%rd Estes*
`extendingacrossthe interval.covereaby two
`c%ose sets).but,thiswas got done to.the extent
`‘-of”:attemptingto--eltiinate-alLspanne&,sets;---
`Zones wi%hout Increasein radioactivityare
`The followingexampleproblemis presented
`easily recogn~zed. On this basis thel@est six .
`-to aia in Understtitingthe foregoingdiscue-
`wells from which logs were closelystutiiedshow
`24 zones a%tenptectfone .clearlymissed?ma frac- Siolls.
`.-
`.turedzones rangingfrom a possible14 to 2?3, or
`
`-EXAMPIWPROBiJIM-’-–’>:-:------------ --:---’-
`
`1.
`
`IWS EXHIBIT 1052
`
`EX_1052_006
`
`

`

`rI
`
`PE-977’
`
`K. R. WEIK$TER,W-C. G
`
`N’S,JR.andS.C. BERRY .
`
`‘
`
`Downloaded from http://onepetro.org/JPT/article-pdf/17/06/619/2218279/spe-977-pa.pdf/1 by Robert Durham on 05 September 2023
`
`gum to reduce friction.
`
`Notes:
`
`If a tracer survey ls,desixed~the
`1.
`frac sand would be radioackivated.The hole
`would be circulatedclean as Step k in the
`procedureand the#mma ray log obtaineaas
`previoupl.yd~scribea. This woula also perm,it
`retrievingthe ball sealersand inspecting
`the “seatmarkstfin determinehole sizej
`shape>.burrcondition,and the number of ball
`that haa been seated?
`2. The surfaceireatlngpressure
`the treatmentmay be calcu-
`expecteclauring
`lated as follows:”
`Pe=,(Pg@)+Pf+Pp-Ph=‘(0.80x3000)+22@150-1560
`=“1210 psi
`where Pg : bot%om-holetreatingpressure
`graclientjpsi[~t
`D= deptht feet
`Pf = frictionpressure>psi [obtainedf,rom
`frac companyhandbook]
`‘ ~ ~ hydrostaticpressiare,psi
`PP ‘ perforationfric%ion,pressbre
`3.
`Hydratiichorsepmierrequiredwill
`be:
`
`,’
`
`P~R
`
`‘=m=—
`
`121OX25~ ./40
`40.8
`
`R = rate, bpm
`
`CONCLUSIONS
`
`2. .Mul.ttstage’ballsealertreatingis w
`economicalana practicalmethod of fracturing
`multipleproducingzone wells providedthe pre-
`cautionsoutltnedin thfs paper are followed..
`2. Multistageba~,,sealertreatingas’
`iescribeaallowsthe use of all the essentials”o,
`good hydraulicfracturetreating..
`.
`j
`‘3. Radioactiveprop aaditivesana tracer
`in evaluatingthe results
`surveysare useful
`of multistagetrea+ingjin refiningthe applica-
`tion in,a particularfield,andin determining
`the qualityof prfmary cementjob subjectedto
`fraclmringoperations.
`r.
`
`ACXNOWLEIXWENT
`
`Z@ authorswish to expresstheir apprecia-
`tion to the Managementof Gulf Oil COW. for
`permissionto publishkhis paper.
`,-
`
`Special.thks are offeredto the following
`Gqlf Oil Corp.persomel: To Jack Evans,
`Jim Agnew and Y. J. Barton for their help &n&
`encouragementiq the.earlydevelopmentot the
`“’mtiti8t%e-tre&ting-out23.ne&--tithis’paper;-and”
`to V. (3;Davis,E. E. ClaplwuabdM. O. “Lisman
`.for,ass$stancein %he latestwork.
`
`.,
`
`.
`
`,’
`
`‘—
`
`Conditions
`
`--
`casing
`J-55
`9.60-lb
`in,
`4.1/2
`qD = 3160 ft.
`to TD. CasingLoa&etiwith drillingmud used to
`displacecement. Treatingvolume~were calcu-
`lated for each zone from core fluid loss ‘test
`data to create70}740 sq ft of area on one wr-
`face of the fracture. All.khe treat.lngfluid>
`i.e.} spearheactand prop fluid}to be LO ppg salt
`water gelledwith 40-lb/1000gal of guar gum and
`mixed with 40-lb/1000gal silica‘flourfor fluid
`loss cont?ol. Spearhe