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SPE 28380

Gi?m

Societyof PetroleumEndrwsrs

Multilayer/Rate Testing in the Cusiana Field, Colombia

J.F. App, BP Exploration (Colombia)

SPEMember

(2

Copyr ight 19S4, Soc ie ty o f Petro leum Eng inee rs , Inc .

Thi s paper was prepared for presentati on st t he SPE 69fh Annual Technic al Conference and Exhibit ion held in New Or leans, LA, U. S.A .,25- 28 September 1 994.

This paper was selec ted for p resentat ion by an SPE Pregram Commitfea fol lowing rev iew of informatkm conta ined in an aba trac f aubmiftad by the author(s) , Con tents o f the paper ,

aa presented , have not been rev iewed by the Sedety o f Patro leum Eng inee rs and are sub ject to correct ion by the author(s) . The mater ia l, as presented , deea not neceaeeri ly ref lect

any pea if ion o f the .Sode ty of Petro leum Eng inee rs , i ts e ff icwa , or members . Papers presentad a t SPE meetings are sub ject to pubf iiat ion rav iew by Edi to rial Committees o f the soc ie ty

of Petrefeum Engineers, Permission toccpy iarestricted to an abstract ofcd more than s00 werda, I lluefrationa may not be c~iad, The abstract should cenfain Conapicuoua acknewladgment

of where and by whom the papar ia preaa ted. Wri te L ib ra rian , SPE , P .0 , Box SSSS3S, R ichardson, TX 7SOfJ2 .-2SSS,U.S.A. Telex , 1S3245 SPEUT.

Abstract

Multi-layertests are performedto identifylayerproperties,such as permeability and skin, in commingled layercompletions. Thie permits improved reservoirmanagement and con@etion optimization.Multi-ratetestsare required to evaluate rate sensitive skin. This paperpresente the resultsof multi-layer/ratetestsperformedonthe two activewells in the Cusiana Field, Colombia. Thetwo wells were the BuenosAires #1, an oil producer, andthe Cusiana #2A-ST, a gas injector. The tests wereperformedby monitoringrate andpressurewith a spinnerand pressuregauge placedabove the lower layer in a twolayer system. These measurements were made atmultiple rates to evaluate rate sensitive skin. Skindetermined from these measurements was used toestimate the upper layer skin and permeability throughsimulations of the buildup and falloff responses.Knowledge of the permeability of the lower layers frompreviouspressure transient tests aided the analyses. Allpressure transient analysis was performed withconventionalwell test analysissoftware.

Introduction

The Buenos Aires #1 and Cusiana #2A-ST wells arelocated in the Cusiana Field of eastern Colombia. Thefield is in the development and appraisal phase andcurrently has one active producer and one gas injector.Bothwells are completed in the Mirador formation. Fieldproduction commenced September, 1992 from theBuenos Aires #1. Production rates averaged 8-11,000STWD with a GOR of 1440 SCF/STB and an API gravityof 34.5. Gas injection,intothe Cusiana #2A-ST, began inFebruary, 1993. All solution gas produced from theBuenos Aires #1 is injected into the Cusiana #2A-ST.Injection rates averaged 12-16,000 MCF/D. The Miradorformationis the mainhydrocarbonbearing reservoirinthe

. -.

Cusiana Field. The top of the Mirador is encountered atan approximate depth of 12,200 ft. SS.with an averagethicknessof 350 ft. Initial reservoir pressure and bottom-hole temperature are approximately6,000 paia (at datum)and 260 “F, respectively. Large compositionalvariationsexist in the reservoir fluid with depth. Consequently, theMirador formation contains a gas cap, volatile oil region

and a black oil region.

The Buenos Aires #1 was drilled as an explorationwelland reached a total depth of 16,000 ft. MD in December,1991. Priorto completion,seven (7) drillstem tests wereperformedincludingthree in the Miradorformation(lower,middleand upper). The initialconyietion interval, a 40 ft.zone in the towerMirador formation,was drillstem testedfrom which a permeability of 1,320 md and a skin of 11were calculated. This interval is considered the lowerlayer in the two layer system. In June, 1993, a 68 ft.section was perforated above the initial 40 ft. interval.

This 68 ft. section is considered the upper layer and isalso part of the lower Mirador. A drill etem test was notperformed in this interval. Both intervals are verticallyisolatedin the reservoir.

Fig. 1 represents an open-hole aamma ray Ioy of thecurrent perforated intervals. Both-intewals are m the oilleg of the Mirador formation. A wellbore schematic isshown in Fig.2.

Productivity History, Lower Layer. Productioncommenced from the initial 40 ft. intewal in September,1992. This initiatedproductionfrom the Cusiana Field.

References and illustrationsat end of paper 1:1

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MULTI-LAYEFWATE TESTING SPE 28380IN TMC el IC I ANA 1313 I I fYll n MR IAI lw I mlb w “”, ”,.” 8 ,L-, VVb -... ”vr .

Four bui!dups performed on this interval between

September, 1992 and January, 1993 ind~ated a trend ofincreasingglobal skinvalues. The cakulated skinvalueswere extremely high, rangingfrom 125 in the first buildupto 175 in the fourth. The causes for the highskinvalueswere believed to be threefold (1) mechanical damageinduced during the completion operation subsequent tothe drill stem tests, (2) partial penetration effects, and (3).*+- aa”ea;.,a -M- ~A=d h b em Ir Ia d h v n n r r .l%wvI a lw OUI ISIL IVW Unls 1, Yw o-m ..l “ -” ” ” ” “ , ..-!. --. -, ,

turbulentflow.

A comparison of the drillstem test skin of 11 to the firstpost-corrpletionbuildupskin (twoweeks after productioncommenced) of 125 is an obvious ind~ator of induceddamage duringthe completionoperation. The suspectedcause for the damage was the loss of 667 bbls ofunfiltered KCL fluid, cast iron bridge plug cuttings andcement to the open perforations.

Partial penetration effects were considered based onproduction log results (September, 1992) indicatingproduction from only the bottom 10 ft. of the 40 ft.perforated interval. Partial penetration effects were notobserved on any of the buildup responses. Simulations,however, showed that wellbore storage (surface shut-in)and the high skin could mask the partial penetrationeffects. The zone was reperforated (March, 1993) in anattempt to obtain a more even flow distribution andreduce the skin caused by partial penetration. Afterreperforating,a skinof 70 was estimatedfrom a buildup.

Rate sensitive skin, caused by turbulence, wasconsidered based on bottom-holeflow rates in excess of

18,000 BPD from a 40 ft. intewal. 1 A multi-rate test

incorporatingthree flow periods and a buildup followingeach flowperiodwas performed in May, 1993 to evaluateturbulence.The resultsof the buildupanalyses suggestedrate sensitive skin.‘The skinvalues ranged from 40 at thelowest rate of 3,300 STB/D to 70 at the highest rate of9,600 STWD.

Skin caused by two phase flow of oil and gas in theresewoir was initiallythought a possibility. However, theminimum measured flowing bottom-hole pressure duringany test was 5,100 psia whmh is 140 psia above thelaboratory measured bubble-point of 4,960 psia. Thebubble point was measured from a bottom-hole sanpletaken duringthe drillstem test operation.

Teat Objectives, Design and Implementation

The multi-layer/rate test in Buenos Aires #1 wasperformed during August, 1993. This was the firstdiagnosticwork carried outon bothcommingledlayers.

Teet Objectives. The test objectives in order ofimportancewere:

1. Evaluate rate sensitive skin and skin values in thelower layer. Skin values from the lower layer wererequiredto monitor a trend of decreasing productivity.Reconfirm rate sensitiie skin as shown by the muiti-rate test.

2. Assess layerflow contributionand productionprofile.

3. Estimate the permeability-thickness and skin of theupper layer, from which the cornbhed permeability-thicknessof bothlayers couldbe determined.

Teot Design. The muiti-iayer transient (MLT) test

technique 2 coupled with a multi-rate test were aaiacted–.–.. .. ... .

10 achieve the first ocqecuve, evaiuate kroiii the skinvaiues and rate sensitive skin in the iower layer. Thebottom-hoiepressures and lower iayer bottom-hole rateswere to be measured by a PLT piaced in the shalesection between the upper and iower iayers. A minimumof four (4) rates were decided for proper analysis of ratesensitiveskin.

A production log tool equipped with a 3.5” fuiiborespinner, quartz pressure gauge, temperature andgradiometer sensors was to be used to assess the layer

contributionand flow profiie as weli as provide bottom-hole rate and pressuredata.

A 24 hour buiidupwas incorporated into the test designfrom which the upper layer permeability and skin wouldbe estimated. Simulationsof the buiidupresponse usinga two iayer modei, with the skin and permeabiiity-thickness of the iower iay r known, wouid provide an

1-stimate of the upper iaye permeability-thickness andskin.The muiti-iayeranalysistachnque couldnotbe usedto estimate the upper iayer permeability and skin due toweiibore mechanical restrictions. Only 14 ft. existsbetween the top of the upper layer and bottom of thepacker tailpipe. Placement of the spinner in this highlyturbulent region wouid have produced faulty spinner

readingsyieidingnon-interpretableor incorrectresultsforthe upper iayer propenies.

The resutts of the two iayer model simulations wouidprovide the combined permeability-thickness of the two

layers.

impiernentetion. The actuai test consisted of fourincreasingfiow rates foilowedby a 24 hour buildup. Eachflow period lasted for approximately seven hours: thisincluded four hours of bottom-hoie pressure and ratemeasurement foiiowed by three hours for spinnerdynamicpasses. Summarized inTabie i are the totai fiowrates, flow rate duration and fiowing bottom-holepressures. For each fiow period, including the buiidup,

the spinnerwas piaced inthe shale sectionbetween bothlayers.

Anaiyeie and Results

Production Log Anaiysis. The spinner results showed65°A of the productioncoming from the iower iayer and35% from the upper iayer. The profiie from the ioweriayer appeared uniformly distributed across the entireperforated intervai. The upper iayer profiie showed thatoniy the upper 32 ft. were contributing. No contributionwas apparent from the iower 36 ft. of the upper iayer.

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Multi-Leyer/Rete Analysis - Lower Layer. The lowerlayer skin va lue s f~~ ea ch of ?~~ @~ ~~!~~ w~~~

calculated by analyzing the measured bottom-holepressure and lower layer rate data recorded by the

apinner (MLT teet technique). A plot of the bottom-holepreseures and lower layer rates is presented in Fig. 3.

The anaiytiial method presented by Odeh and Jones,3superpositionanalysisto evaluate rate sensitiveskin,wasused to cakulate the skin values. The only unknownvariable was the skin, as the permeability of 1,320 mdwas well established from previous buildups. The ratehistory used for the Odeh-Jones analysis included twomonthsof productionpriorto the multi-layerhte test. Anextrapolated pressure of 5,801 psia, obtained from apreviousbuildup,was used for the analysis.

The Odeh-Jones plotof the four flowingperiods isshownin Fig. 4. The increase in the intercepts with rateindicates increasing skin as is indicated on Fig. 4. The

calculated skin values for each rate are also listed inTable 1. The skinvalue increasedfrom a value of 70 afterreptmforetiiigto a maximumvalue of 107.

Fig. 5 represents the calculated skinvalues versus rate.Assuming a linear relationship between skin andturbulence,

S= S+Dq . . . . . . . . . . . . . . . . . . . . . . . . . . . . (1)

a mechanical skin of 42 was estimated fromthe intercept

and a turbulence factor on the order of 10-2 (STWD)-lwas estimatedfromthe slope.The largeturbulencefactorsuggestsa strongnon-Darcyflow componen?.T!M cau.%

for this could be turbulence, two phase flow or acotiination of both. Two phase flow wee consideredbased on a lighter fluid system (higher GOR) in thecommingledintervals.

For comparison purposes an analysis of (Pi-P~)/q vs q

was pedormed. This method also assumes the linearrelationshipbetween skinand rate as shown in Eq. 1, endassumes that Pi-P~ varies linearlywiththe square of the

rate based on the followingrelationship:1

Pi-P~ = Aq+ Bq2, . . . . . . . . . . . . . . . . . . . ...(2)

where the coefficientsA and B come from the transient

solution to the radial diffusivity equation in an infiniteresemoir. This anafysis uses a single flow rate for eachmajorflowperiodin comparisonto the MLT test techniquewhere instantaneous rates are used. A mechanical skin

of 53 and a turbulence factor on the order of 10-2

(STB/D)-l were cakulated using this method. Thesevalues compare well with the values obtained from theOdehdones analysis.

Prior knowledge of the lower layer permeability wasessential to obtainingreliableskin values from the Odeh-Jones analysis. A knownpermeebilii fixes the skpe ofthe finedrawn througheach flowperiid. Due to the datascatter apparent in the Odeh-Jones plot, calculation of

both the permeability and skin of the lower layer wouldhmm h a r m n #r n qg@ ~fl~~~a,,”. ” ““”, , “n ., -,,

Buildup Analysis - Estimation of Upper Layer

Permeability end Skin and Composite Perrnaability-Thickness. A log-log derivative plot of the buildup

responseisshown inFig. 6.4 Highlightedonthe pfotisapartial penetration effect. This is consistent with theproduction log results showing no contributionfrom thelower36 ft. ofthe upper layer. A radialflow regionis alsohighlighted on this plot. This is, however, a late timeeffect and not the middle time region representing thenear welfborepermeabifii-thickneee from both layers. Anoverlay of a buildup from onfy the lower 40 ft. in Fig. 7illustrates that the middle time region occurs at earliertimes and ismaskedby the partialpenetrationeffect.

The masking of the middle time region presenteddifficultiesin determiningthe upper layer permeabilityand

skin. However, an estimation of the permeability-thicknesswas made from the late time rad~l flow region.Assurrptions criticalto this estimationwere (1) constant,,mma,-t,-. R*Am- :-= -, A4,.qha ...4...- -4 :-..--*:-wv=~ c=J=IPI~-rtl== VUI IV t!1=1=UIU=u! IIlV_*@i~fi ofthe late time region, and, (2) the cumulativepermeabiliithickness of a dual layer system as calculated from abuildup is the sum of the individual layer permesbility-thicknesses. Cakulated from the log-log derivatives inFig. 7, the two layer system has a permeakWy-thckneseof 45,000 md-ft as conpared to 34,000 md-ftforthe lowerlayer in this region. The permeability-thickness of theupper layer was estimated to be the difference in thepermeabilii-thickness values, 11,000 md-ft.

It wee notpossibleto estimatethe skinof the upper layer.

Simulations,usinga two layer model,were attemptedbuta wide range of skin values were found to match themeasured data. Consequently, a meaningful value couldnotbe determined.

The combined permeability-thicknessof both layerswasestimated at 63,800 md-ft, the sum of the permeability-thicknesseefor each layer.

Reeulte Summery - Buenos Airae #1

1.Skin values were determined and rate sensitive skinwee confirmed for the lower layer. A large non-Darcyflow component exists. Rate sensitiie skin, including

estimates of the mechankal skin,were verMedby twoindependent methods. Knowfedge of the lower layerpermeability from previous buildups was critical incakulating the skinvalues.

2. A continuedtrend of increasingskinvalues withtime inthe lower layerwas identified.

3. The productionprofile was established from the PLT

dynamic passes. The lack of production from thelower 36 ft. of the upper layer caused the partialpenetrationeffecton the buildupresponea.

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4 MULTI-LAYEFURATETESTINGINTHE CUSIANA FIELD, COLOMBIA

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SPE 28380

4. The upper layer permeability-thicknesswas estimatedfrom the late time radial flow region throughconmarisonwith a previousbuildupresponsefromthe

low&lay&. The skin of the upper interval could notbe reliily estimated.

5. A composite permeability-thickness of 63,800 md-ftwas determinedfromthe buildupanalysis.

Rev& of ~

Well History. The Cusiana #2A-ST well was sidetrackedfrom the originalCusiana #2A well due to casingcollapse.A total depth of 14,219 ft. MD was reached in November1991. The well is completed across the entire Miradorformation in the gas cap in three perforated intervals.These perforated intervals are highlighted on an open-hole gamma ray log in Fig. 8. A wellbore schematic isshown inFig. 9.

- . . .L .?——,-———,.,-— AL-- 4.:114-— .--, - .-----rnor 10 me nnal corrqxenontmree mu! wem t e sm wer e

performed, includingone in the upper and lower Miradorformations. The upper Mirador test evaluated the upper60 ft. of the Mirador formation fromwhich a permeabiliiof 3.5 md and a mechanical skin of 7 were determined.The lower Mirador drill stem test evaluated the lower 100ft. (net pay of 98 ft.) ofthe Miradorformationfromwhichapermeability of 108 md (kh = 10,585 md-ft) and amechanicalskinof 10 were calculated.

Gas injectionbegan in February, 1993 intothe two upperperforated intervals. A packer with a plug locatedimmediatelybelow the middleintervalpreventedgasfrombeing injectedintothe lower layer. The plugwas pulledin

May, 1993 allowing gas injection into the entire Miradorsection.

The Miradorwas considereda two layer systemfromthe—..,., --. -”_.._- ._-. ---1..-:- -* --A--:-. m-. --- L:l&,mum-ralellayer 18s1analyws wanupwm. r o r mma u r m y -

thickness was the criteria for this distinction. As isillustrated in Fig. 8, the middle perforated interval (60 ft.)was considered the upper layer and the deepestperforated interval (100 ft.) was considered the lowerlayer. The shallowestperforated intewal (110 ft.) was notconsidered in the analysis as it contains only 1% of thetotal Miradorparmaability-thickness.

Mufti-Ftetdlayer Test

Calculation of a turbulence factor through multi-ratetesting was the primary objective of the Cusiana #2A-STtest. Knowledge of the turbulence factor was necessaryto make injectionrate predictionsforfuture injectionwells.Determining the injectivitypotential of the Cusiana #2A-S? was also a reauiredobiective,The MLT test technique_7—..–—-–a–-.for skin estimation of the uppar and lower layers wasconsidered secondary. This was based on the concernthat the rates determined by the spinner would besuffiiientiy noisyto precludean accurate analysis.

Baaed on these considerations, the objectives of themulti-rate/layer testing in Cusiana #2A-ST in order ofi~ortance we~

1. Determine the turbulence factor. Evaluate injectivitypotential by calculating the combined permeability-thicknessof both layersand the mechanical skin.

2. Establish the injectivityprofile between the upper and

lowerlayers.

3. Atterr@ to estimate globalskinforthe lower layer andbothpermeabilityand globalskin for the upper layer.

To achieve these objectivesa multi-ratetest incorporatingfour rates followed by a 46 hour falloff was performed.The MLT teat technque was incorporatedby placing thespinner above the lower layer. This w“ou id p rov id e t iie

means for calculatingthe skinof the lower layer. As withBuenos Aires #1, the permeability-thicknessof the lowerlayer was knownfrom a drillstem test. Once the skin ofthe lower layer was eatabliihed, a simulationof the falloffpressures with a two layer model would provide the skinand permeability of the upper intewal. The same PLT

toolas was usedfor the BuenosAires#1 testingwas alsousedfor the Cusiana #2A-ST test.

The multi-ratdlayer test was performedduringNovember,1993. The test consistedof four increasinginjectionratesfollowed by a 48 hour pressure falloff. For each flowperiod, includingthe falloff,the spinnerwas placed abovethe lower layer immediately below the isolation packer.Dynamic passes and stationary stops were made duringonlythe maximum injection rate of 16,000 MCF/D. Eachinjection rate lasted between six and nine hours exceptfor the final rate which was extended due to operationalreasons. Fig. 10 illustratesthe rate and pressure historyfor the test. Summarized in Table II are the injectionrates, rate duration, injectionbottom-hole pressures and

globalskinvalues.

Review of Analysis and Reeutta

Production Log Analysis. The production log results(dynamic passes and stationary stops) indicated that88”70of the gas was being injected into the middle andlowerperforated intervals.The remaining12% of the gaswas being injected into the top 40 ft. of the uppermostperforated intewal. Virtually no gas was being injectedintothe sand-shale sequences in the lower 70 ft. of theuppermostperforated interval.The injectioncontributionsfor each intewal are noted on Fig. 8.

Falloff Analysis. Derivative analysis of the falloffresponse determined a permeability of 94 md (14,100md-ft) and a global skin of 114. A reduction inpermeabilityto 45 md was detected at a radial distancefromthe wellboreof 1,550 ft. Fig. 11 representsa log-logderivativeplotsimulatedwiththe above parameters using

a radiai composite reservoir modei. The iarg~ @ iniiie---— ----

simulated derivative response is due to the analyticaltreatment of large skinby the pressure transient analysissoftware.

The permeabilityof 94 mdwas estimated based on a netpay of 150 ft. Net pay was selected onlyfrom the middleand lower perforated intewals (upper and lower layers).This was based upon core and drill stem test data

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indicating that nearly 99% of the well permeability-thickness, 13,886 md-ft., is contained within theseintervals.The permeabilii-thicknass of the top perforatedinterval(110 ft.) is estimated at 214 md-ft.from core and

drillstemtest data.

A permeabilityof 67 mdwas estimatedfor the upper layerbased on net pay of 52 ft. This was determined bysubtracting the lower layer permeability-thickness of10,585 md-ft from the conposite permeability-thwknesscalculated from the falloff derivative analysis of 14,100md-ft.

Turbulence. Turbulencewas confirmedthroughanalysisof the injectionpressures for each of the four flow rates.Two methodswere usedto estimatethe turbulencefactorand mechanical skin: (1) conventionalgas well analysisthrough a plot of (~.Pinj)/q vs q, and, (2) superposition

analysis of the four injection periods using an Odeh-

Jones plot. A turbulence factor of 1.Ix10-3 (MCF/D)-land a mechanical skin of 96 were estimated from thesemethods. Turbulence factors of this order of magnitudehave been notedfrompreviousgaswell drillstem tests inthe Cusiana Field.

Upper and Lower Layer Global Skin Estimations. Thelower layer global skin was calculated by analyzing thebottom-hole pressure and spinner rate measurements.Similar to the Buenos Aires #1 analysis, the onlyunknownvariable was the skin as the permeabilityof thelower layer was cakulated froma previousdrillstem test.AnOdehJones plotwas constructedfromwhicha globalskin of approximately 160 was cakulated (Fig. 12). Notethe large degree of data scatter inthe Odehdones plot.

Rate sensitive skin was apparent from the Odeh-Jonesplot, however, the calculated skin values for eachinjectionperiodvariedvery little. The large value for skinis attributed to mechanical damage induced during thecompletion operation, turbulence and partial penetrationeffects. The spinner resultsshowedthat the bottom30 ft.of this intervalwere notcontributing.

An upper layer skin value of 60 was estimated through

simulations of the faiioff pressure response with a twolayer model assuming nocrossflowbetween layers. Theparametersused inthese simulationswere an upper layerperrnaabilii 67 md and a lower layer permeability andskinof 108 mdand 160, respectively.

Due to the extreme data scatter inthe Odeh-Jones plot,the skin estimates for both layers are only qualitative

assessments, However, on a relative basis the lowerlayer is more severely damaged than the upper layer.Furthermore, calculation of the lower layer permeabilityfrom the Odeh-Jones plot would have been irrpossibledue to the data scatter.

Resutta Summary- Cusiana #2A=ST

1. The turbulence factor and the injectivitypotentialof theCusiana #2A-ST were determinedby analyzing the fourrates and the falloff.

2. The injectionprofilewas established.

3. Estimates of the lower and upper layer global skinvalues were obtained but are considered qualitative

due the to data scatter. However, on a relative basisthe lower layer is more severely damaged than theupper layer.

General Conclusions

1.

2.

3.

4.

5.

The MLT test technique coupled with multi-ratetestingachieved the primary test objectives. Individual layerskin and permeebilii estimates were made for bothwells with the exception of the upper layer skin inBuenosAiree#1.

Knowledge of the permeability of one layer from aprevioustransienttest simplifiedthe MLT test analysis.This reduced the unknown variable to only skin andfixed the slope through each rate on the OdehJonessuperpositionplots.

Analysis of both the lower layer permeability and skinusing bottom-hole rate and pressure data (MLT testanalysis) was not considered reliable due to theextreme data scatter.

The buildup(Buenos Aires #1) and the falloff (Cusiana#2A-ST) were requiredfor estimatingthe upper layerproperties.

-Conventional well test analysis software wassuccessfullyused in analyzingthe MLT teat data.

Nomenclature

A = definedin Eq. 2B = definedin Eq. 2

D = turbulencefactor, (STB/D)-l or (MCF/D)-l

Pi s initialreservoirpressure,psia

PWI= flowingbottom-holepressure, psiaPIII!= injectionbotio~hoi~ MSSU rQ, Sk

t 2= productionrate, STB/ or MCFS = globalskinS = mechanicalskin

Acknowledgments

The author would like to thank BP Exploration forpermissionto publishthis paper.

References

i. Duong, A.N. .0“infiowPetiorrnance Relationshipsfor OilWells withRate Dependent Skkr: PetroleumSociety ofCIM paper 86-37-37 presented at 1986 PetroleumSociety ofCIM, Calgary, June 8-11.

2. Kuchuk, F.J., Karakas, M., and Ayestaran, L.: “WellTesting and Analysis Techniques for LayeredReservoirs,”SPEFE (Aug. 1986) 324.

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3. Odeh, A.S. and Jones, L.G. : “ Pressure DrawdownAnalysis, Variable-Rate Case: JPT (Aug. 1965) 960-964 Trans., AIME, 234.

4. Bourdet, D. et d: “Use of Pressure Derivative forDiagnosing Pressure-Transient Behavior; JPT (Oct.4nncl\4mnnI000] I Lou.

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Tabla I - Buenos Aires #1, Fbw Rates& Duration, Fiowiig BHP, Global Skin (Lower Layer)

Rate Fbw Rates* Duration ywyp Global Skh

(SW) (l-IRS) (Lower Layer)

1 3,740 7.8 5,622 67

2L!Annu,- 7.4 K A= Qi

3 8,400 7.2 ;:% 1“;

4 10,300 11.5 5,101 107

q Commingled flow rates from both layers

Tabla II - Cusiana #2A-ST, Injection Rates& Duration, Injection BHP, Global Skin

Rate Injection Rates Dumtion Injection BHP Global Skh(MCF/1)) (1-fRs) m)

1 6,900 9.2 5,906 107

2 6.0 5,969 110

3 1?% 6.0 6,019 113

4 16,000 21.9 6,119 114

q Commingled injection rates from both layers

m.o o.

m APIo. 300.0

GR API

Fig.1 - BuenosAires#1 Open-Hole Gamma Ray(depthdivisionsrepresent25 ft.).

BUENOS AIRES 1

4vYnmma

*mcsowoE

r I.MR SHOE

-nilF

3w “C,aSm E

[111

-lhr—

~

3Fig. 2- BuenosAires #1 Wellbore schematic.

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MULTI-LAYEFURATETESTINGIN THE CUSIANA FIELD, COLOMBIA

L +L *

pMwwww+*++++++ + +

S@ MO . no . sm . 6m.

Moo .

(4000 . f “’mm - ro, , , , , ,

SW. MO. S20. S30. MO. 660. se a

lime (hrs)

Fig. 3- BuenosAkes #1, bottom-holepressureand lower layer rate historyfromspinner.

0.11

0.10

0.06

0.06

0.07

0.06

Q= 6,~5 S-, S= 107

x

Q= 5,440ST~, S= lW

++

Q . 4,1s0ST~, S= 61

#

t , , I ,

1. 2. 3. 4. 5. 6.

su~ositionlq

Fig. 4- BuenosAires#1, analysisof lower layer skinusingOdeh-Jones analysisand MLT teat

technique. Increasing interceptsindcate increasingskinwith rate.

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120-

100-

so- ,

$ so.

401k----

20 -

0.

0 1000 2000 Sooo 4000 Sooo 6000 7000

Rate (stb/d)

Fig. 5- BuenosAires #1, skinvs. rate for lower layer. SkinvaluesobtainedfromOdehJones analysis.

+

Fig. 6- BuenosAires #1, derivativeplotofbuildup.

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10 MULTI-LAYEWRATE TESTINGINTHE CUSIANA FIELD, COLOMBIA

SPE 28380

+

+x+

;A

+ ‘i MULTI-LAYER

+x % BUILDUP* A ,

“ 4

xxm

1 /DRFV lf 3US ~~!~ p lNCfiEA8ED. -------

10 4la +

e,

,0 4 ,Oa 10-2 10-~ 10 0,0 1

dt (hr)

Fig. 7- BuenosAires #1, overlayof buildupperformed duringMLT testwith previousbuildupof only lowerlayer. Indcates increase inpermaabNty-thicknessbased on late time radialflow region.

>11

s J r h

I I D 1 1 1 1 1 u 1 I

CUSIANA 2A-ST

WJlllir

laYo.coQwoE~ II I I

00#CSWIOE.~

Fig. 8- Cusiana # 2A-ST Open-Hole Gamma Ray Fig. 9- Cusiana # 2A-ST Wellbore schematic.

(depth divisionsrepresent25 ft.).

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q

SPE 28380 J.F. APP 11

6ZO0

6100

++

++ ++

m +++++ L ++++++++++

S7001 t c

1s00. lsae. 1s40. 1s60. l am.

1600. 1s20. 1s40. 1660. 1660.

T im e (h e)

Fig. 10- Cusiana # 2A-ST, injectionrate (bothlayers) and bottom-holepressurehistoty.

Radial Composfte Homogeneous Reservoir

[v-

lj XXm

xx,,well.starage= .0149BBLB/PBl

-.Sk in {per t ) = 114,

/

,. -X., 5’

psrmesbility = 4S.0MDxx. Ps rm .(i nn er ) = 9 4.0 MD:. InnerRadius = 1SS0,FEET%‘.

+“ %. InitialPressure= 6761,P81X.‘.

x

\

‘,‘.‘.

:

‘1 xx

x&#ii. ----

:‘.,,---- --”-~&/’

x‘----

10-4 10-3 10-2 10-1 100 101

dt (hr)

Fig. 11- Cusiana # 2A-ST, simulationof log-logderivativeof falloffwith radialcompositemodel.

181

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.,

Q-.3,7ss Imlm

MO 3.00 3.s0 4.00

!31mUnn9i I ian/a-r -r ------- _

Fig. 12- Cusiana # 2A-ST, Odehdones plotof iower iayer MLT test data.

00028380

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