,—_– -.

Gii!Be’ m

. . .

].%xietyofl%t roleum Engineers_..l

SPE 35991

Development of a Stimulation Treatment Integrated ModelK. M. Barlko, SPE, and C. T. Montgomery, SPE, ARCO Exploration and Production Technology and C. L, Boney, SPE,and V. L. Ward, SPE, Schlumberger Dowell

Copyright 1996 society of Petroleum Engineers Inc

This papef was prepared for presentation at the Petroleum Computer Conference held in

Dallas, Texas 2.5 June 199S

This paper was selected for presentation by an SPE Program Commdtee following rew.w of

mformat)on contmned m an abstract Submnred by the aumor[s) Contents o! the pap.w as

presented have not been reviewed by the Scc@y of Petroleum Engineers a“d ara subject to

co frectfon by the author(s) The mater! al, as presented does not necessarily reflect any

pcmtlon of the So.aety of Petroleum Engineers !ti off!cers m mambers PaWm presented at

SPE meetings are subpct to publlcatm” rewew by Ed,tonal Comrmttee.s ot ttw Society of

Petroleum En~lneers Perrnrssm” to copy m restricted to an ●bstraci of not more than 300

words IIlustratlons may “ot be copied The abstract should contain con%p!cuous

acknowledgment of where and by tiom the paper was presented Wrtte Llbrarran SPE P O

Box 833636 Richardson TX 75063.3636 U S A fax 01214.952-9435

AbstractPast publications have indicated (hat matrix (rcatmcnt failuresarc in the order of 30%0 To improve the succcss rate formatrix trcatmcnis, current work has been on real time fieldmonitoring These systems calcrda(c the evolutlon of skinduring matrix stimulations, However, these systems can onlyinform you how your treatment is performing. A need for asyslem that op[imixes fluids prior to pumping is needed sotha( an cnginccr can take trot advantage of monitoring acidtrcatrncnts.This paper dcscribcs the dcvciopmcnt of an integrated matrixstimulation model for sandstone and carborratc formationsthat assists in determining formation damage, selection andoptimization of fluid volumes, provides a pressure skinresponse of the acid treatment and forecasts the bcncfrt of the[rcatrncnt. The model includes three expert advisors for (henovice cnginccr, a kinetic based multilaycr rcscmoir rnodcland a geochemical model to dctcrmirre rock fluidcornpatability problems. Additional modules that providesupport for the user arc a scale predictor, critical drawdown,ball scaler forccas[cr and a fluid database for the selection offluids and additives. A production forecast rnodulc isincluded 10 forecast the bcnctit of the stimulation,

IntroductionFormation damage can occur from nalural or inducedmechanisms that reduce the capability of flow between theformation and the near wellbore region, (bus giving a rise to apositive skin. To mitigate this damage, matrix technologyusing rcactivc and non reactive fluids are pumped into the

formation. StimCADEm (Stimulation Treatment IntegratedModel Computer Aided Design and Evaluation) wasdeveloped as an integrated software application used toidcn(i~, prevent and mitigate formation damage. The goal ofStimCADE is to optimize stimulation treatments, rccognizcfailures and maximize job success.

Within ARCO, matrix stimulation treatments fail toimprove productivi~ in one out of three treatments]. Asummary of these failures is shown in Table 1. The currentpractices for selecting wells for matrix stimulation arcevaluating well production/injection histories. offset WCIIperformance and pressure transient analysis. Designtechniques to improve the wells pcrtormance arc based on‘rules of thumb’,

To improve ARCO’s matrix treatments a real timemonitoring systcm’ was dcvclopcd based on Paccaloni 2’3andProvost4”~ tiork. This teehnique calculates a transient or

“apparent” skin w. time as shown in Fig. 1. The adaptationof this tcchniquc has improved the area of incorrect fieldprocedures. Since then several authors have expanded onthese ideas by calculating a derivative skin vs. timc6 andusing an inverse injectivity plot ““*as diagnostic tools.

To prevent the usc of the wrong fluid, Expert systemswere developed by ARC09 and others 10-13. However, thesetools were based on rules of thumb, providing no analyticalsolutions. Past cxpcricncc indicates that knowledge systemsare often discarded by the engineer after a fcw uscs and haveonly found utility as teaching tools. To overcome thislimitation, and to circumvent the loss of cxpcrtisc within theindustry, the expert systems provided within the ncw softwarearc integrated to an analytical model.

This paper examines how to optimize matrix treatmentsusing an integrated design strategy. This softwtarc utilizesexpert systems Iinkcd to analytical acidizing simulators alongwith several peripheral tools to achicvc the optimizedtreatment.

Approach

StirnCADE is an integrated program designed to allow theuser to enter data, calculate and obtain results, Figure 2

75

2 K.M.6artko, C.T.Montgomery,C.L. Boney,V,L.Ward SPE 35991provides an overall schematic of the system, Movement i.e. they cannot be used to determine the effectiveness ofthroughout the program is consistent with Microsoft” solvent systems.products for ease. of use. The tool and status bar (Fig. 3) ispresented when the user opens the application. Several of themenus are typical of other Microsofi o applications. The threedistinct menus to this application are 1) StimCADE, 2)Current Module., and 3) Tools. By pulling down theStimCADE menu the eleven available modules shown inTable 2 are displayed. Upon selecting a module the adjacentmenu item becomes active within that application. The thirdmenu Tools provides access to the consistency checkeroptions, variable editor, unit management, graphics andreports. Navigation throughout the module is performed byselecting the appropriate buttons. The application is built sothat a user can randomly move from one panel to the next.

The program status bar is at the bottom of the screen. Thestatus bar provides the user with information about the activefield. The information provided is the input data, whether thefield is calculated or input, locked or unlocked entry, if thefield is consistent and if the enty is calculated or userentered, If the user inputs inconsistent data the user has theoptions to change the inconsistency or continue.

Help is provided within the application by selecting thequestion mark in the menu bar or pressing of the F1 key whenthe cursor is active in a field. Upon selection of the questionmark the user is provided help for the entire application, Ifthe user selects F1, the help for the specific field is opened.Information within help provides the user with hints on inputparameters.

There are four levels built into the application as shown inTable 3, The first level is called the “Xerox or photocopymode”. This mode minimizes the design work for the user byusing the experience gained on previous matrix treatments.The user simply opens a previous data file, changes the wellname and completion properties of the wellbore and theprogram calculates the new displacement and treatmentvolumes. The second mode uses artificial intelligenceadvisors to build a fluid schedule based on industry ‘rules ofthumb’, The system interrogates the user to determine thesuitability of the well for treatment (Candidate SelectionAdvisor), damage type (Formation Damage Advisor) andtreatment type and volume (Fluid Selection Advisor). Neitherthe ‘photocopy’ and ‘advisor’ modes provide optimization orreal time analysis. The third mode consists of athermodynamic/kinetic model which optimizes the scheduleby running the simulator through a series of time steps andexamining the resultant

Module Description Advisors

Three advisors which have been written under the Nexpertshell, are provided for the user, The first advisor is theCandidate Selection Advisor (CSA), The CSA helps a new orinexperienced user determine if the well is a suitablecandidate for stimulation and whether the user shouldpreceed with a matrix treatment or a propped fracturetreatment. This is determined by running a quick darcy flowcalculation or using the production forecast module.Additional questions are centered around basic wellknowledge and information from a pressure transientanalysis. If damage cannot be determined the user is advisedto perform additional diagnostics on the well such as Nodalanalysis.

The Formation Damage Advisor @A) asks a series ofquestions and determines up to 18 damage mechanisms asshown in Table 4. The FDA knowledge is based on in houseexperience and ref. 14. This advisor is also built to suggestadditional diagnostic work to further define the damage. Forexample, if a water analysis is not available the programsuggests that it be obtained before proceeding. If analysis isavailable, then the user has the option to open the scalepredictor module,

The Fluid Selection Advisor (FSA) is the third advisorand is provided to determine treatment fluid type and volume,This advisor requires a damage type which can be obtained byrunning the formation damage advisor or directly input by theuser. The expert system requires that the user has knowledgeof the reservoir. The FSA uses industry experience and ‘rulesof thumb’ 1617to determine the fluids and volume required.The schedule is then imported into the schedule panel forfurther refinement using the kinetic models.

The fourth mode is the most difficult level, requiring theuser 10 know the damage mechanism as well as the chemicalinteraction of the trca{ment fluids and the rock. This modeuses a geochemical model to determine when and wheresecondary reaction precipitation occurs from the treatment, Askin vs. volume and time plot is provided by these two modes,Both modes are applicable only when reactive fluids are used

Matrix DesignThe matrix design consists of three modules - Pump ScheduleGenerator (PSG), Acid Placement and GeoCHECK,

The pump schedule generator is a 14 single phase designmodule for matrix sandstone and carbonate acidizing whichaddresses wormholing. The function of this module is tooptimize the fluid and diverter volumes based upon a damageradius or reduction of skin. The skin is either input per layeror calculated based on prosity or flow rate per layer. Whenrunning the PSG, step objectives per layer are required, Thestep objectives are based on fluid invasion or live acidinvasion requirements. The result of this module is anoptimized schedule based upon a skin reduction vs. time orvolume 18, Diversion of acid is accounted for during theoptimization of the treatment schedule. The model canpredict diversion for particulate, foam, ball sealers and

76

SPE 35991 Develornnentof a StimulationTreatment Integrated Model 3

maximum rate. This is the same for the acid placementmodule. The user either accepts this schedule or can cancelthe results and keep the previous schedule.

The Acid Placement 19”23module is a 1d, 2 phase, tinitcdifference simulator which allows multilaycr contlgurationsup to 10 Iaycrs for computing pressure and skin evolutionduring matrix acidizing. Mineral dissolution is simulatedusing a 9 mineral, three acid (HC1, HF. Fluoboric acid) modelwhich accounts for reaction kinetics, Local porosity changeduring acidizing is correlated to a local permeabilitymodification and finally an overall damage skin per Iaycr,

The rock/ftuid simulator (GeoCHECK) 24-25 is a 1-d,single phase tinitc difference geochemical model that alsopredicts skin reduction but more importantly the precipitationof acid by-products, The geochemical model has beentailored to acidizing by reducing the input to two acids, HCIand HF. and 8 minerals. The acidizing equilibrium chemistryaccounts for approximately 14 elements and over 100 spccics.

Ball Sealer PlacementThe Ball Sealer Placement simulator handles conventionaland buoyant ball sealers, For conventional ball sealersz’ boththe ability of the bail scaler to scat on a perforation, and tostays in place arc evaluated For buoyant ball sealers,28 theplacement velocity in the wellbore is evaluated against thebuoyant velocity, The result of the module determines if theball scats and stay in place. A typical output screen is shownin Fig. 4, The ball scaler module is a stand alone tool that canbe used to perform sensitivity analysis. The module is alsoused in the acid placcmcnt module to determine the pressureincrcascs duc to placcmcnt of the balls. Currently thesimulator is good for vertical wcllbores.

Scale PredictorThe Scale Predictor 29-7(’model uses the same chemistry as theGcoCHECK model cxccpt that it is tailored to scaletendencies. The model is a batch chemistry model which canhand]c ttvo fluids and accounts for bicarbonate and COJ

evolution, The scale model is accessible through FDA or as astandalone module. An example of the input panel is shownin Fig. S. The scale model currently identities eight scales(Table 5).

Critical Drawdown - Perforation and Reservoir FailureThe Critical Drawdown predicts the maximum sand freeproduction rate for a given WC1land the maximum reservoirdepletion prior to subsidence, The primary components of therncthod arc prediction of rock strength, calculation ofmaximum drawdown for perforation stability and rcscwoirfailure. The program uscs correlation’s from Morita 31 andWcingartcn 3: An example of the output of the model ispresented in Fig. 6.

Producti& Forecast and EconomicsThe Production Forecast 33-34model is a single layer reservoirmodel allowing partial completion, dual porosity andpermeability anisotropy. Reservoir depletion duringproduction is taken into account, The Production Forecastmodel is coupled to an economic module (o predict NPV andpayout based on the new skin predicted from the acidplacement module.

DiscussionTo test the performance of StimCADE various input data setshave been run. An example run is presented here and isbased on information obtained in ref. 35. Inpu[ data andinformation are shown in Table 6, The well has foursandstone intervals with skin damage varying from 455 to 38.

To determine the skin per layer production data was inputinto the skin analysis window. This window calculates a skinbased cm porosity, production/injection or by directlyinputting a value. The PSG is executed to optimize thetreatment based on damage penetration and skin change. Theexample shows that reduction of skin to zero was notachieved. The simulator warned the user at the end of thesimulation that the treatment objective was not achieved andthe user either accepts the new schedule or cancels. For thisexample PSG provided a pump schcdulc as presented inTable 7.

To determine the effects of the treatment, the acidplacement module is opened and cxccutcd. A summary of thetreatment results are presented in Fig. 7. A final skin of 5.6was obtained from the treatment. However, the model alsolndicatcd that the final stage of clay acid was probably notnecessary duc to minimal improvement in skin. Severalgraphs are provided to the user to visually interpret thesimulator results. Two of these graphs arc prcscntcd in Fig 8and 9.

Figure 7 shows the change in skin per layer by volume ofacid pumped. The graph indicates that layer 4 requires

additional acid to remove the remaining damage. To fullyoptimize the treatment, the user needs to usc a di~crting agentto place additional volumes of acid to the lower layer,

Figure 8 is a graph showing the bottomhole pressure and

rate vs. volume of acid. The acid placement simulator cancalculate a maximum rate based on the fracture gradient orbased on a maximum surface pressure or pump rate. In thisexample the rate was maximized to the pump rate. The graph

indicates that there is plenty of room to incrcasc the pumprate. A higher pump rate could have helped in placingadditional acid into layer 4.

As can be seen through this example, additional runs willfirrc tune the fluid volumes required to treat the well Tocomplete the fluid schedule with additives the user wouldopen the fluid editor, choose the vendor da[abasc and map thefluids to the suggested additives, A customer report can begenerated or imported into the user’s word processing

program for further customizing.

77

4 K.M.Bartko, CT. Montgomery,C.L. Boney, V,L.Ward SPE 35991StimCADE Future AdvancementFuture enhancements of the application and majorimprowmrents of the StimCAf)E application will come from aTechnology Development User Club (TDUC). The TDUCwill act as a consortium to guide the evolution of StimCADEthrough funding of major upgrades and new applications.The club dctcmlincs the use of membership fees in funding orpartially fhrrding major upgrades, new applications andresearch, It is intended to tap the knowledge of all users tocontinually improve on the application with the intention ofmaking it a standard in the industry

Conclusions1, Ncw software and computer capabilities have allowed thedevelopment of a PC based matrix simulator.2. Integrated technology for designing matrix treatments andreal (imc monitoring was not previously available.3. The future usc of this tool will improve the success ofmatrix stimulation treatments.4, Expertise and economic improvement of matrix treatmentscan continue to evolve by using StimCADE as the ultimatetechnical documentation.5. An easy to use tool is provided to field personnel toimprove matrix treatments.6, Industry involvement in the application and futureirnprovcmcnts are provided through a “TechnologyDcvclopmcnt User Club.

AcknowledgmentsWe thank the management of ARCO E&P Technology andSchlumberger Dowell for permission to publish this paper.Wc also thank the StimCADE Team and CAPSHERTechnology for writing the program.

“StinlCADEmi” M a registered trademark of SchlumbcrgerDowcll,“Microsofi”mr’ is a registered trademark of MicrosoftCorporation.

References1.

2.

3

4.

5

Montgomery, C. 1’,, Jan, Y-M., and Niemeyer, B. L.:“I)evclopment of a Matrix-Acidizing Stimulation TreatmentEvhdion and Recording System,” SPEPF(Nov. 1995)219.Paccaloni, G.: “New Method Proves Value of SimulationI’lanning” [)11& Ga.YJ. (Nov. 19, 1979) 155.Paccaloui, G : “Field I iistory Veriiies Control, Evaluation” Oil

& Gas J. (Nov. 26, 1979) 61.Provost, L. P. and Economidies, M. J~:“Real-Time Evalution ofMatrix Acidizing Treatments,” J Pehdewn Sci. & Errg. ( 1987)

1, 145.Provost, L. P. and Econornidies, M. J.: “Applications of Real-Timc Matrix Acidizing Method,” SPEPE (Nov. 1989) 40 I;‘1’runs.,AIME, 287.

6

7

8

9

10

II

12

13

1415

16

17

18

[9

20

21

2223

Behenna, R.R.: “interpretation of Matrix Acidizing Treatments{Jsing a Continuously Monitored Skin Factor,” paper SPE2740 I presented at the 1994 SPE Formahon Darnage ControlSymposium, Lafayette, Feb7-10,1[ill, AD. and Zhu, U.: “Real-Time Monitoring of MatrixAcidizing hrcluding the Effects of Diverting Agents,” paperSPE 2854t? presented at the 1994 SPE Annual Conference andExhibition, New Orleans, Sept.25-28Zhu, D.smd Hill, AD : “Field Results Demonstrate EnhancedMatrix Acidizing Through Real-Time Motoring,” paper SPE35197 presented at the Permian Basin oil & Gas RecoveryConference, Midland, TX,,March 27-29.Blackburn, R., Abel, J. ,and Day, R.: “ACLDW-AcidizingDesign with an Expert System,” paper presented at the 1990Conf on AJ in Petroleum Exploration and Production, CollegeStation, May 15-17.Van DomeIon, M,, Ford, M.S., W.G. F., and Chiu, T. J,: “AnExpert System for Matrix Acidizing Treatment Design,” paperSPE 24779 presented at the 1992 Annual Technical Conferenceand Exhibition, Washigton, DC Oct. 4-7.Chiu, T, J., Caudell, EA. and Wu, F.L,: “Development ofExpert Systems to Assist with Complex Fluid Dmign,” paperSPE 24416 presented at the 1992 Petroleum ComputerConference, Houston, TX. July 19-22Cram, R.S,, and Ilendrickson, AR.: “ArI Investigation into theApplication of Expert Systems to Matrix Design)” paper SPE15602 presented at the 1986 Annual Conference andExhibition, New Orleans, LA, Oct 5-8.Matteine L., Coserrza, G. Paccaloni, G. and Beranger, A.: “AKnowledge Based Approach to Matrix Stimulation,” paper SPE20966 presented at the Europec 90, T?re Hague, NetherlandsOtt. 22-24.SPE Repn”nt Series No. 29 Formation Damage.

McLeod, HO.: “The Planning, Execution and Evaluation ofAcid Treatments in Sandstone Formations,” SPE paper 1I931I’resented at the 1986 hnual Technical Conference andExhibition held in San Francisco, CA. ,Oct. 5-8,Kamkas, M. and Tariq, S M,: “Semi-analytical ProductivityModels for Perforated Completions, paper SPE18247,prescnted at the 1988 Annual Conference andExhibition, l{ouston, TX,Oct.2-5.Bertaux, J.: “Fluid Selection Guide to Matrix Treatments,”Doweli Schlumberger, 1988.Surnotarto, U., Flill, AD., and Sepehrnoon, K.: “An integratedSandstone Acidizing Fluid Selection and Simulation toOptimize Treatment Design,’ paper SPE 30520 presented atthe 1995 Annual Technical Conference & Exhibition Dallas,TX Oct. 22-25.‘Ilomas, R. and Faanin, V.: “A Sandstone Acidizing Simulatorfor Engineered Treatment DesIgnsA Field Study,” paper IPA93-23.122 presented at the 22nd Annual Convention, Ott.93.Toubal ,1;.: “A Matrix fnjection Simulator,” The Mathematicsand its Applications Conference Series, flx~ard University

Press, NY ( 1992), 767,

Piot,B,, and Perthius, I i.:’’Matrix Acidizing of Sandstones,”Reservoir Stimulation, Schlumberger Educational Services,1987Schector: “Oif We// S(imcdation,” Prentice Hal], 1992.Perthius,H, Toubal, E. aod Piot,B.: “Acid ReactionSandDamage Removal in Sandstones: A Model for Selecting theAcid Formulation,’’paper SPE 18469,presented at the 1989

78

SPE 35991 Development of a StimulationTreatment Integrated Model 5

24

25

26

27.

28

29

30

31

32

33

34

35

S1’11lad S\mposium on OIIliclci Chemistry, I louston, TX, Feb.n-lof:ogler, 1I S., Lund, K and McCunc, C C, ‘Predicting theFlow and Rcact]on of I [CM [F Ac]d Mixtures in PorousSandsknw Cores,” .$I’W(OCI 1976) 248-60 ;Irms, e.il.111i,261.I.und,K and Foglcr, 1I S “Acidizing V. The Prediction of theMovmncnt of Acid and f’urncabdity fronts InSa]]dstol]cs,’’(”)t,,n~./]g,g$cici.(1976)31,381-92McCunc,C C , Foglcv, 11S., and Ault, J w,: “A Ncw Model ofthe I’hys].sal and Chemical Changes in Sandstone E)uringAcidizing,” W’}ll(oct 1975) 361-70.lhnwl,R.W., Neill, (i. ] I , and Lopm,R.G “Faclors Influencingoptlmom f+all Scaicr f]erformancc,” JPT (April 1963), 450-454C,abriel, (;.A. and Erbstoesscr, S,R,, paper S1}ll 13085presented at the I‘)X4 Annual “fcchmcal Conference and}khibi[ion, I IoosIon, TX , Scpt 16-24.l.i, Y-I [.: ‘Theories of Chemical Equilibrium Calculations forPR( J Watdlood Geochemical Modeling and ARC() ScalePredictor,’ ARC() ReporI RR 95-()(]13, May 1995.

LI, Y-1I., Crane, S.1). and Coleman, J K., “A Novel Approachto Predict the Co-Prcclpitatlon of BaS04 and SrS04,” S1’1129489 prcsentml at the S1’11Production C@ations Symposium,[)klahoma Ci[y, OK April 2Jl, 1995,Morita, N et.al , “A Quick Method to [)etwrninc Subs] dcnccRcscrwolr Compactma, hi-Situ Stress Induced by Rescrvo]rDcplctlon>” JPT (Jan 1989).Wciogarten, J.S. and Perkins, “r.K ,: “Prediction of SandProduchon in C,as Wells Methods and Gulf of Mexico CaseStudies,” SPE paper 24797 presented at the 1992 AnnualConference, Washington, D.C., Ott. 4-7I [urst, V.Il.. The Applicahon of the Lap]ace Transform toFlow Problems in Ikservmrs,” Trans. ALifE, Vol 186, 1949,305-324.Mathews, R.: “Pressure Testing Build-up and FIOWI‘rest mWells,” SPE Monogrf7ph Vol ISchaible, 1) F , Akpan, 13,, and Ayouh, J., A,: “Identifictition,I:valwlt{om and Treatment of FormatIon Damage, Offshorcl,oulsltina,” paper SP1l 14820 presented at the 1986 SPES!mposlum on Formation l)amagc Control, [,afaycttc, I.A,Feb 26-27

I Table 1- Reasons For Failure IReason ] Failure Number I 0/0 of Failures 1

] Incorrect Field I 27 I 34 IProcedure 1Incorrect Design I 30 ] 38

Wrong Fluid ] 22 I 28

I Total 1 79 I

I Table 2- Available Modules

General

Candidate Selection AdvisorFormation Damage Advisor

Fluid Selection Advisor

Pump Schedule GeneratorAcid Placement

GeocheckProduction ForecastCritical Drawdown

Scale PredictorBall Scaler

Table 3- Design Levels

XeroxAdvisor

Empirical/KineticGeochemical Based

Table 4- Formation Damage Types

Drilling MudClay Swelling and Migmtion

Emulsions

Scales

Water BlockNettability Changes

ParatT_rr/Asphaltene DepositsMixed DepositsIron Hydroxide

CorrosionUnfiltered Solids

BacteriaFluid Loss Pills

Table S - Scale Types

Calcium CarbonateIron Carbonate

Magnesium CarbonateCalcium Sulfate

GypsumStrontium Sulfate

Barium SulfateIron Sulfide

79

6 KM. Bartko, CT. Montgomery, C.L. Boney, V.L. Ward SPE 35991

Table 6- Input Summary

# Layers 4Frac[ure Gradient 0,8 psi/ftWell Radius 8.8 inType Of Gravel PackCompletionResemoir Pressure 5580 psiBottomhole 210 ‘FtemperatureWell Spacing 160 acreDamage Type Fines MigrationPermeability 526 mdKh/Kv 10 mdDamage Radius 30 in

Mineral Composition UndamagedQuartz 75 %Calcite 5 %Feldspar 10 %Kaolinite 3 %Smcctite 2 %Illite 4.5 !40

Chlorite 0,5 ‘%0

Mineral Composition DamagedKaolinite 40 %Smectite 30 ‘?40

[Ilitc 430 ‘YO

SkinLayer I 39Layer 2 147layer 3 70Layer 4 455

Table 7- Output Summary

Fluid Cum. Damage Liquid BHP Over(bbl) Skin Rate (psi) Frac

I [ (bpm) ] I Press

5%HC1 790 74 2 ] 6000 I No

12%HC1/3% HF ] 1419 I 8.5 2 I 5660 ] No 12% NH’rcl 1789 8.5 2 5660 No

Clay Acid 1927 5.76 2 5646 No

2% NI-Lcl 2075 5,67 2 5646 No

10

t0 —--- ——. . –+—.—+ -

02040 f4801w ,20,4Q,,xI,8020D?20 mTim b Mlm.da

Fig. 1- Skin vs. Volume

DATA INPUT I CALCULATION IC.* F— D-..,- ,-- A.. yhp

‘L=?.k.fi !!!!!!9

~w~

Fig. 2- StimCADE roadrnap

El-—-[-,

RESULTS

❑iii

P7

s.k..

‘c’- =n..,, . V-

Ip

Fig. 3- StiwrCADE opaning screen.

80

SPE 35991 Development of a Simulation Treatment Integrated Mcdel 7

Fig. 6- Critical Drawdown Surrurrary Output Wkrdow.

Fig.4.- Output Panel for Ball Sealer Module. This particular caseshows that all ball sealers will seat on the perforations

,m

I \

1- ,=,J’J--=j‘1

\ q H

+-– I-i,- - -..................,.,....0 ,7< m ,,,, ,4,, ,,,,

Fig. 7- Skin vs. Volume. The maximum skin change occurred afterthe first mud acid. Only marginal improvement seen with thesecond stage of clay acid..

‘m

T r –. ~. ~—— .–T- T—,

,,,

Fig 6. - Scale Predictor Input Panel. Scale predictor can run withone or two fluids mixed. A sensitivity analysis of percent fluid,pressure and temperature can be made by selecting the sensitivitycheck box,

P

‘-’[l‘-,* I }– ‘“”-1-=’;-’1---1---1-–4--‘- “,m -—

~:_.-.l..l.....1 1 \_.._iJ,. >m“ ,!B la! ,ml,

“-H,

Fig. 8- BHP/Rate vs Volume. The model was run with constant ratechecked.

81