...Jc.PTbJ-o2-D3 The Relationship of the Westerose D-3 Pool

:_r to Other Pools on the Common Aquifer

By JOHN HNATIUK* and J_ W. MARTINELLI** ,.,· .. _,,i<:: -:-

(18t/l. Annual Technical Meeting, The PetTOleutn Society of CIM, Banfj, Alta., ilfay, 1967) Downloaded from http://onepetro.org/JCPT/article-pdf/6/02/43/2166126/petsoc-67-02-03.pdf by guest on 24 September 2021 ABSTRACT A study of a 70-mile chain of prolific Leduc D-3 reef pools situated on a common aquifer is presented. The primary objecth·e of the study was the prediction of the future performance of the centrally located 'Vesterose D-3 Pool, as influenced by other pools in the trend. A two­ ': dimensional mathematical model of the Acheson-Homeglen .j Rimbey Leduc D-3 reef chain was del'eloped. Values of re­ j sistance and capacitance, characterizing reservoir para­ meters, were assigned to the grid points in the reservoir ALBERTA simulator_ These were adjusted until a satisfactory match with twenty years of performance history -was obtained_ The future pressure performance and water influx or efflux under many combinations of producing rates were predicted for a ten-year period. The study indicated unu­ sual trends in pressure and water influx behaviour result­ ing from interference effects- Further movement of Weste­ ACHESON_ ~0DMONTON rose oil into the underlying aquifer was predicted with HOMEGLEN- ~ continued injection of produced solution gas. These results were instrumental in the recent termination of gas in­ RIMBEY --; jection into the \Vesterose D-3 PooL The study also pre­ D-3 REEF dicted the withdrawal rates necessary from the 'Vesterose CHAIN D-3 Pool to maintain the oil-water interface at its current position and to control its further movement. • CALGARY

INTRODUCTION HE Westerose D-3 oil and gas pool is located in T the Acheson-Homeglen Rimbey chain of prolific Leduc D-3 reef pools situated in central Alberta. This Figm·e 1.-Location illap of the Acheson-Homeglen Rimbey D-8 chain of pools extends from a point near Edmonton, Reef Trend. southwesterly for a distance of over 70 miles, as shD\\"11 on F'igure 1. .- : -. Predictions of the future performance of the \Vest­ erose D-3 Pool necessitate studies of the reservoir ;.._::'· __ characteristics, past performance and future produc­ ...... tion rates for all the major pools in the trend sharing R JW5 RJW5 the common aquifer. The eight major hydrocarbon accumulations in the trend are the Acheson D-3A, Leduc-Woodbend D-3A, Glen Park D-3A, Wizard Lake D-3A, Bonnie Glen D-3A, Westerose D-3, Westerose South D-3A and Homeglen-Rimbey D-3 pools, shown on FigU1·e 2. The figure also shows the areal extent of the porous Leduc - Cooking Lake aquifer on which these reef pools occur. The smaller pools have, for study pur­ poses, been included with the main pools near which they are located. The Golden Spike D-3A Pool, al­ though a major accumulation, is not considered in this study, as the pool is not in pressure communication with the other pools in the trend . . ' - ___:_] +=·The British Anz.etican Oil Company, Ltd_, Calgary, j Albe>·ta. +:·*Gulf Resea1·ch and Development Co1npany, Pitts­ Figun 2.-Pools in the Acheson-Homeglen Rimbey D-8 Reef T1·end_ bu'tgh, Pa.

Technology, April-June, 1967, Montreal 43 HlSTORY GEOLOGY The first of the major D-3 pools to be discovered in The Acheson-Homeglen Rimbey Leduc D-3 reef the trend was the famous Leduc-\Voodbend Pool, loc­ trend consists of bioherms or isolated reef buildup~. ated in 1947. After six years, more than 500 producing overlain b.v calcareous shale and underlain by a frng­ wells had been completed in the pool on 40-acrc spacing. mental reefal limestone platform. The oil and gas ac­ In 1950, the Acheson Pool was discovered and subse­ cumulations are underlain by the common Leduc - quently developed ·with 89 producing wells. The ~'izard Cooking Lake aquifer, 'vhich provides pressure com­ Lake and Glen Park oil pools, now containing 52 and munication between the pools. Figm·e S is a profile 11 wells, respectively, were discovered in 1951. These of the Acheson-Homeglen Rimbey reef trend, showing \'v'ere follo\ved by Bonnie Glen in 1952, which now con­ the gas and oil columns and the relative ~ubsea posi­ tains 163 D-3 \\'ells. tions of the major pools. The \Ve.sterose D-3 Pool wa~ discovered in August, The \Vestero!:ie Pool is a dolomitized bioherm reef; 1952, with the drilling of B.A. C.P.R. Five!and 4-3-46- it is fossiliferous, \o,.·ith numerous variable-sized vugs 28W4, which encountered the Leduc D-3 at 6,852 feet and fractures . .i.\'lost of the cures are characterized by ( 3,908 feet subsea l. The well encountet·ed 253 feet of vugs, from pinpoint to several incheH in diameter, of gas cap and 238 feet of oil zone containing 42" API both the solution and organic type. The porosity and gravity oil. The pool was developed with nineteen pro­ permeability are variable, but there are no indications ducing wells on 80-acre spacing. within the reef of any extensive or continuous zones of Downloaded from http://onepetro.org/JCPT/article-pdf/6/02/43/2166126/petsoc-67-02-03.pdf by guest on 24 September 2021 The thick Homeglen-Rimbey reef, with its thin oil uniformly low porosity. The reservoir has an extensive column, was discovered in Ma.y, 1953, followed by the network of interconnected fractures, solution channels discovery of the prolific \Vesterose South gas pool in and vugs, resulting in high permeability both later:~lly 1954. and vertically, and, consequently, high well prodm·­ tivities. All pools have been produced as oil poolg except \\'esterase South, which tontained no oil column. Pres­ The extent and thickness of the porous Leduc - Sll re maintenance schemes have been in operation in Cooking Lake aquifer ,.,.·ere mapped after examining Ledur-\Voodbend since L955 and in Acheson since data from approximately 300 wells which penetrated 1957. Produced solution gas \\'as re-injected into the the Cooking Lake. The extent of the total Leduc. - \Vesterose Pool during the period from July, 1955, to Cooking Lake poro!:iity is shown on F'iauTe :2. The September, 1966. Gas production commenced from the porosity continues se,'eral miles east of the D-3 reef \Vesterose South and Homeglen-Rimbey Pools in 1961. trend. but is very limited to the west_ The southern and northern limits of the porous aquifer are um~er­ tain and have been somewhat arbitrarily selected for this stud}•- The aquifer could continue fal'ther to in­ clude the i\:Iorinville D-3 reefs to the north and the Sylvan Lake D-3A reef to the south. The volume of water contained in the aquifer was calculatecl to be 75 billion barrels.

RESERVOIR CHARACTERISTICS The \Vesterose D-3 Pool originally contained 158 million STB of oil in the 238-foot oil zone and 117 Bcf of raw gas in the gas cap. The average porosity is 9.34 per cent in the oil zone and 7.95 per cent in the ga!:i cap. The aYerage horizontal and vertical per­ meabilities are 1,934 md and 195 md, respectively. The connate water saturation is estimated to be 7 per cent. The initial pregsure at discovery w.as 2,56tl psig at -4,280 feet datum, the reservoir temperature 178°F, and the formation volume fact01· 1.45. c:::J- GAS []J[IJ-OIL EJ-WATEA Table I t:ompares the reservoir characteristics of Figuro J.-Profile of the Ache.sOJI-Homcg(en Rintbey the \Vestet·o.!'le D-3 Pool to those for the other D-3 Leduc Recj Trend. pools in the trend.

TABLE I COMPARISON OF HESERVOIR PARAMETERS-ACHESON-HOMEGLEN Hl"!IlEY D-3 REEF TREND

Porosity "','(' Permeability Oil iu Gas ---- Md. ,\faximwn Place iu Depth Oil Gas Cnmwte ------A..tw Tnlal Million Plan~ Pnol Feet Zone Cap Water t;;, Horiz. Vert. Acres Pay Barrels Bcf ------· ------Acheson .. 5,076 9.1 75 10 3.100 1.500 3.640 23-t 149 10 Leduc-Wooc~ l-end. 5.3·14 8.0 7.4 15 1.000 5-100 21.600 232 30i\ ·120 Glen Park. .. 6.30-! 9.6 - 7.6 1.60-1 105 -!:13 -1.21 28 Wizard Lake. 6.458 9.-1 - 7 700 n.a. 3.250 6.6 380 Bonnie Glen. ... 6.995 9.4 8 ..3 6 350 Il,:l . 8.800 'ill 625 4:10 \Vesterase ... 7.233 93-! 7.95 7 1.93-1 195 1.757 589 158 117 \Vc.sterose .Sourll. 7,740 - 8.6 10 1.200 60 10,720 673 0 1.915 Homeglen-Rimbcy. 7.934 7.6 7.S 10 250 72 14,053 553 110 1.285

44 The Jcurnol of Canadian Petroleum ·-·--

,: ~:~

=I 2.100 I M 0 ~~~~mt= 11144~1~ ~ ' o~IL~ .to.' o1L ~ndo. ~ -4212.·6' 6 ' ....., r- ~ ~ 4 ... - ~ 2 cyM. 0IL P~OOj .. ~ 1 1 ' 1 .... 1 4 O~IL~ A~G. G~S ' -4399 :.J r- .... -4411·5' 3 r 2 \ ~. ., I ... ~- L- ... _... C~M-fA~ IN~. I Figw·e 5.-0riginal and czn·J"ent positions of fluid 0 L inte1·jaces in the Weste1·ose D-3 Pool. 19!5'2 54 " " 60 " 64 1966 (August, 1966)

Fig1n·e 4--PerfonJiancc history of the lVesterose Downloaded from http://onepetro.org/JCPT/article-pdf/6/02/43/2166126/petsoc-67-02-03.pdf by guest on 24 September 2021 D-8 Pool.

WESTEROSE POOL RESERVOIR PERFORMANCE The Westerose D-3 Pool has exhibited excelle.nt per­ formance since being placed on production in August, 1952. The performance history of the pool is illus­ trated graphicalhr on Figu.re 4. Recently, the 6,000- B/D allowable has been produced from only six of the nineteen productive ,'\.~ells. Maximum production for the pool has been 8,000 B/D, well below the estimated potential of the pooL The gas-oil ratio has remained .:;, . constant over the producing life of the pool at ap­ proximately 650 cf/bbl. Production to the end of 1966 represented 13.2 per cent of the original oil in place. The pressure decline over the fifteen-year period has been just less than 300 psi. As a gas conservation measure, and to increase the ultimate oil recovery, 10 Bcf of produced solution gas Figm·e 6.-ReservoiT simula.toJ• gJ·id for the Ache­ were injected into the Westerose gas cap during the son-Homeglrm Rimbey D-8 Reef Tnnd. period from August, 1955, to September, 1966, at ., which time injection was terminated to reduce the efflux of oil into the underlying aquifer_ The dominant producing mechanism in the Weste­ Companlr's IBl\oi 360 computer, as British American's computer in CalgarJ.~ did not have sufficient capacity. rose D-3 Pool is a verJ.~ efficient gravity segregation drive. A centrally located fluid-interface observation The reservoir simulator is a t\'i.'o-dimensional com­ '"'ell was completed in 1965. Gradiomanometer surveys puter program which simulates the pressure-pi-educ­ indicate that the gas-oil interface had moved down­ tion performance of a pool or series of inter-related ,,.·ard 51.6 feet and the oil-water interface do·wnward pools. When the past performance can be satisfactor­ ·~ 12.5 feet, as of August, 1966, leaving an oil column ily matched using the computer model, future pres­ ~ r of 199 feet. F'igU1·e 5 illustrates the original and cur­ sure performance can be readily forecasted. .... rent positions of the fluid interfaces. l\oiaterial balance In developing the reservoir simulator or computer calculations based on production-pressure histor}• and program, it is necessary to reduce the actual three­ ·'' the recorded fluid interfaces indicate that the ultimate dimensional reservoirs to a two-dimensional network recovery of oil from the 'V' esterase D-3 Pool will be in which each element or grid block simulates the 77 pel' cent. fluid capacitance and the resistance of a corresponding RESERVOIR SIMULATOR PROGRAM reservoir volume. A grid network comprised of 1,050 mesh blocks was imposed over a geological map of A forecast of the future performance of any one the pools in the Acheson-Homeglen Rimbey trend, as ..··; pool located on a common aquifer requires a knowledge shown in Figure 6. 107 of the mesh blocks were used of the past performance and future behaviour of the as segments of oil and gas reservoirs underlain by other pools with which it is in pressure communica­ water; others simulated only segments of the aquifer. tion. Early in 1965, a study was undertaken by Brit­ A large number of mesh blocks fell beyond the limits ish American, with the assistance of Gulf Research of the aquifer and were assigned no capacitance or & Development Company, to provide forecasts of the resistance. Volumes of the rock, oil, gas and/or water, future performance of the '\Vesterose D-3 Pool under multiplied by their respective compressibilities, were various conditions. This type of study would have assigned to each grid block, analogous to the capaci­ been performed on the electric analyzer prior to the tance in the electric analyzer model. Resistances in ~ advent of the digital computer. The digital computer each of four directions were assigned to each mesh r·. now provides a rapid means of running a great many block as functions of the fluid viscosity, thickness, cases which can be readily updated periodically. The permeability and dimensions of the grid 'block. A Acheson-Homeglen Rimbey trend reservoir simulator component to represent withdrawal or injection from study was performed on Gulf Research & Development the block was also required.

Technology, April-June, 1967, Montreal 45 ''~.-~~~~~--.-.-.--r-.--.-c-.--r-.~r->-~lsc·r ot.TE I l L.• " ,------, ~:.!~~u - ... I - "I-~ g I '-k?ALCD PRESS R q I ~Z~UD I ~t·+-r------~ , -----f -~Di- 'r Z450 1 --/------z5: ' I RECO~OED PRE "SJS..: - ~ I j : "'z~uo w -}--- .. _,.!'WATER INFLUX 0:,; I q- -q I I ~:::r-- J) y~[- ~t::! a22~0 I I.,~,. J_J_ --- -~--5~

0 ~::::~ Tftl--: -- I __ -- ~ :; FIGURE 9 ! . - --~~ "! ~ z 100 PRESSURE MATCH B. WATER INFLUX _j ___ _ -1.:~=- ·~. ~~ 1 - BONNIE GLEN POOL i:: q qo : 0 l LD5D I -15 10~o'19~ 1I19~Z 19=~ ~~=~ 19=~ 19~ 19'711958 1959 191>0,1961 19s.

kh"Y Downloaded from http://onepetro.org/JCPT/article-pdf/6/02/43/2166126/petsoc-67-02-03.pdf by guest on 24 September 2021

Fiuw·e 7.-R(~prcscntation of a rcser­ 'I!Oir simulatm· mesh block. citance and resistance were successi\'ely adjusted until a satisfactory match was obtained between the cal­ culated and measured pres~ures. Thirty-five compu­ The interdependence of adjoining mesh block!:i can ter runs \o,.·ere made before a satisfactory match wn~ be 1·epresented by a set of equations ba::;ed on the fun­ obtained. · damentals of Kirchhoff's Law that the algebraic sum In the process of making· the necessary adjustment.!-!, of the flow rates (currents) directed toward a junc­ ::;omething wa.s learned about the relationship betweeu tioH point is zero. This priuciple is illustrated in Fig­ pools. For example, it was indicated, and later con­ ure 7. The unsteady-state flow equation is then \\Tit­ firmed by computer runs, that the pools north of Bon­ ten for every mesh block in the simulator, which leads nie Glen have very little influence on Bonnie Glen and to a set of simultaneous equations that can be solved the pools to the south. rapidly on a digital computer. The pressures for each of the mesh blocks are determined at each time step The computer model was further adjusted in 19G7 from the solution of these equations, and a printout b}• incorporating t\'•.. ·o additional :years of production of the a\·erage pool pressures by time periods is ob­ and pt·e::;sure history and more current production tained. A t:alculation to determine the ,,rater influx or forecasts. This updating added two years of gas pt·o­ efflux w~'s performed by the computer at the end duction history to the four years previously available of each year. for the \'Vesterose South and Homeglen-Rimbey pooh~. Minor adjustments to the capacitance were necessary PRESSURE 'MATCH during eight additional computer runs. Pool pressure histories, as recorded over the past Figu·re 9 shows the comparison between measured twenty years, \\'ere converb~d to the \Vesterose datum and calculated pressures for the Bonnie Glen D-3A of --4,280 feet and plotted. These pressure history plots Pool to the end of 1966. Also included are the cumu­ are shown on Figzwe 8. A.fter calculating the ap­ lative water influx volumes by years. Figure 10 is the propriate capacitances and resistances for the mesh pressure match and calculated water influx for the block~. prior production and injection volumes to the \Vesterose D-3 Pool to the end of 1966. Although some end of 1964 were assigned to mesh blocks by quarter discrepancy exists in early years, a close match has years. The computer then calculated a pressure his­ been obtained over the last five years. Figure 11 tory for each pool, plots of which 'vere compared to shows the pressure match and water influx volume for the plots of actual pool pressures. Values of capa- the nearby \Vesterose South Pool.

2600 ' "' 1 • .1-D?c·v. DArE ~ 0 F:o ~~~f-~~-:-'tc-"-"11.~-~-ID--+-+--1--j------;

~ mo I I I I ,..::_---"- . - .,~ ~ RECORDED PAE'sS~~ --.-.k--CALC D PRESS ~ ~ 2."100 ~ "" -r 1 1 ...+-t-i-t,- ,_~~--r- -., ~ ~ 2!~0 ____ _ I , ..J .... ] __ o ~ ~ 1 §~ 2.300r---r-r-r-t-r-+-+­ a 0 ~ 2.2.00 of--+--f---l~f--+--

~ 2150 ~ ~ ~.... 2.100 ~ FIGURE 10 GAS INJ ~ .._ ::?, z100 PRESSURE MATCH & WATER INFLUX T~A!! D-j-_ -~ ~ E • WESTEROSE D-3 POOL 1 ~ zo~o o '-' • 195ZI1953 1gS"' 1355 135E 19~7 19'B 19!9 1960;19 61 196'Zil963 19E4 196'3 1966

Figm·c S.-PrHJL pressure histol'ies in the Acheson­ Figure 10.-Prcssm·e match cmrl wafcl· iujlux jo1· Homeglen Rim[H?y D-.'? TTcnd. the T·Vesterose D-9 Pool_

46 The Journal of Canadian Petroleum TABLE II FORECAST NET RESERVOIR WITHDRAWAL RATES ACHESON-HOMEGLEN RIMBEY D-3 REEF TREND

(Thousand Barrels :~=er Day)

I Leduc- Glen Wizard Bonnie Weslemse Home glen- Acheson Woodbend Park Lake Glen U'esterose South Rimbey ,.. 1967. _,, ...... 2.4 1.7 1.2 14.2 26.4 6.3 217.0 135.3 1968, ...... ·-··· 2.2 1.4 L1 15.5 27.0 6.4 225.0 140.1 1969 ...... ·----- 2.2 0.7 1.2 17.6 29.5 7.9 235.0 145.4 1970 .. .. . ····· . 2.4 0.5 1.3 19.5 32.7 8.8 248.0 151.5 1971 ...... 25 0.2 1.4 20.8 34.9 9.3 257.0 157.9 :·: -. 1972 ...... ·- .... 2.6 0.1 1.5 22.5 38.0 10.3 270.0 165.0 ,,"" 1973 ...... 2.6 - 1.5 22.2 38.0 10.4 284.0 172.8 1974 ...... 2.6 - 1.6 23.4 40.0 ILl 298.0 181.6 ; _..-- .,:~ - 1975 ...... --- 2.7 - 1.7 24.4 41.7 11.8 3150 191.2 ..:1 1976 ...... 2.7 - 1.8 25.4 43.1 12.4 334.0 201.9 '

:.,Downloaded from http://onepetro.org/JCPT/article-pdf/6/02/43/2166126/petsoc-67-02-03.pdf by guest on 24 September 2021 ,. ., These computer water influx results should be con­ PREDICTION CASES ,)., sidered as qualitative rather than quantitative and are Future pressure performance and water influx over ~ subject to revision as additional performance becomes available and an updated model is 'utilized. The in­ the next ten years were predicted by the reservoir dicated water influxes could, in part, be due to addi­ simulator for all pools. The two basic cases examined tional hydrocarbon reserves not yet proven by drilling were with and without re-injection of solution gas and thus not included in the model. A more exact water into \Vesterose, assuming, in both cases, a variation influx can be calculated using measured interface in oil allowables above and below our best estimates. movements or a more exact material balance. In most A third set of predictions for all pools assumed various instances, the measured influxes, where available! withdrawal rates from the Westerose Pool, with other agree reasonably well ·with the computer values. pools remaining at forecast rates. A fourth set of pre­ dictions assumed \Vesterose withdrawal rates to be a I At the conclusion of the pressure historj• matches, I fixed percentage of the forecast allowablesJ with other ,. it was of interest to examine the terms in the equa­ pools at forecast rates. Other cases were run, shutting tions for capacitance and resistance and to compare in one or more pools to determine the interference these values to those originally assigned to the model. effects. 1-, The review indicated effective aquifer permeabilities in the order of 1000 md south of Acheson! reducing to Table II shows the forecast reservoir withdrawal 250 md immediately south of Wizard Lake and in­ rates assumed in predicting pressure performance. creasing again to 400 md in the region of Homeglen­ Rimbey. PREDICTION RESULTS It was evident from the pressure matches that all The predicted performance of the Westerose D-3 pools on the reef trend are, to varj•ing degrees. in Pool! \.;:ith and without continued re-injection of pro­ pressure communication through the underlying aqui­ duced solution gas! is shown in Figu,re 12. In this fer. The Bonnie Glen and Westerose pools are in par­ prediction! all other pools produce at forecast rates. ticularly good communication. Termination of injection will result in a 21-psi de­ The results confirmed the indications from the in­ crease in the Westerose pressure over the next ten terface observation well that an efflux of oil has oc­ :vears, but will decrease the cumulative efflux of oil curred from the \\'esterase Pool into the underlying aquifer. 230 0 -

'"'' DISt'Y. DATE !L!:_GAS PROD. 0 .... I I I COMMENCED "~ 225 I 0 ~ - " 1 ..-CALC D. PRESS. '-' :::::,...... JITH IINJ. 0 ~ "t 220 PRk~ ~ \ 0 ~ l, ~ 0 NO INJ. y ~ 215 0 ... - 0 + I I PRESS_ ...... r...... ::: RECORDED 210 0 0 ~ "' + "~ !{\_ ~ I'.k'WITH INJ. ,_ 0 ~"' 2050 - WATER I NFL )<:: ,... / ~ ~ .. 0 - -I 0 ~ CUM. WATER EFFLUX ~ 1'... ~ ~200 \ ~ 0 -,. ' ;;._._ ~ ll; ~ 0 - t:! 195 0 FIGURE II "'~ - PRESSURE MATCH S. WATER INFLUX -' --40~ " 0 1900 _, WESTEROSE SOUTH POOL \ 1967 1968 1969 1970 1971 1972 1973 1974 1975 1976 ,., 0 -so 1953 1954 195511955 1957119!58 1959 19£0 1961 1962]196'3 1964 1965 - '"' Figw·e 12--P·redicted Performance - Westerose -··-..-·£. Figure 11.-PnJssure -match and water injlu~ for Pool - with and without gas in.jection - all pools the Westerose South Pool. at forecast rates.

Technology. April-June. 1967, Montreal 47 by 3_;3 million barrels o·ver the period. Termination of Various withdrawal rates from the \Vesterose Pool, injection will not, however, completely eliminate future as a percentage of forecast rates, were also considered. losses of oil into the aquifer. Figure 13 shows the The results are shown on Fignre 16. It was noted that present pressure profile along the Acheson-Homeglen over the next ten years, a withdrawal rate equal to Rimbe~r reef trend compared to that for the end of 115 per cent of the forecast rate would tend to main­ 1976, assuming no gas injection at \Vesterose. tain the oil-water interface near its current level. A Figur-e 11,. shows the \Vesterose performance when \Vesterose withdrawal rate equal to 200 per cent of the oil production for all pools is 75 per cent, 100 per cent forecast rate would be required to return the oil-water and 125 per cent of forec-ast rates, all assuming no interface back to its original position over the next re-injection of gas at \Vesterose. These curves could ten years. be used for interpolation if actual production rates Table III .summarizes the predicted p1·essure per­ differ from those forecast. It may be noted that the formance and cumulative water influxes under variou::~ effects of oil pt·oduction are not very significant to conditions fur the \Vesterose Pool and the adjacent tht~ YVesterose water efflux, if all pools change propor­ Bonnie Glen and \Vesterose South pools. tionately. In view of the predicted continuing efflux of oil Figure 15 sho,.,.-s the pel'formance of the \Vesterose from the \Vesterose Pool with continued re-injection D-3 Pool, with no gas re-injection, holding all pools at of gas, re-injection was terminated in September, forecast rates, but increasing the \Vesterose withdraw­ 1966. Periodic interface mea~urements and updating als to 10,000, 15,000 and 20,000 reservoir barrels per of the reservoir simulator study are necessary to con­Downloaded from http://onepetro.org/JCPT/article-pdf/6/02/43/2166126/petsoc-67-02-03.pdf by guest on 24 September 2021 da,·. It is indicated that the \Vesterose withdrawal firm that the efflux of oil is continuing, even after rates should be maintained at 10,000 B/D in order to termination of injection. Should efflux of oil continue, maintain the oil-water contact near its current level it may be necessary to remove limited volume~ of ga~ over the next ten years. The withdrawal rate must be from the gas cap to arrest the efflux. maintained at 18,000 B/D in order to bring the \V'este­ ro;;e oil-water contact back to its original position in ten years. The 10,000 B;D withdrawal rate would cur­ rently correspond to 4,600 B/D of stock tank oil plus 2300 - 3.2 MMcf of gas per day.

----4 ~ 2€00 ' r--- -0-;1~~~1~-,7 ------!1 ':;: ~2.1501-----t ;;:~ 00 I ~ CU~R ENT' 1--/ ' ...- § 2100 I--"'~ • / ...... / ...... "' 0:~00 ";;; ,_,.... ~ < PREDICTED ~ 2050 I'-/I -- AT 12.·31-76 "- ~ 2000 < ~ ~ 2000 / ~ ~ -•< I i\ - 1800 ~ ' -- ~ ~:.:: "'t::l ...., ~ ~).. l~ ~ ~ 3 ~ g 3 ~ < IEQQ r-~:t:-:;;s--lt,--~--~-~--~--~-s:- " lu~ ~-:c ~ !!: cr: <: ::::. "'{ ...., -•< ~it lJ<., !3 ~ ~ ~ ~ ~ ~ :t:: '=: :!:: ctl '=: \:1 -.I )..

~ 2300 2300 +30 ~ b ~2250 ~ ' ~ '

c:~ 0 " "'~ -5 ~

-10 ...~ 1'976

Fig'il/'l' 15.-Prcdicted Performance - lVestM·ose f'igUJ'f' 16.-PJ·edict('d Pe1·;orma11Ct' - ll't•,qft•rosc Pool - WestcJ·o.se at 11arious rcservoir rates - all Ponl Wcstel·ose jorec"ast rate i11cn·a:wd other pools al fon•cast rates. all ollteJ• pools at fon•cast.

48 The Journal of Canadian Petroleum TABLE ill RESULTS OF RESERVOIR SIMULATOR STUDY-ACHESON-HOMEGLEN RIMBEY D-3 TREND ''' ' (Pressures in psig at -4,280 ft and Cumulative Infh.L" in miilion bbl)

WESTEROSE C.4SE WESTEROSE BONNIE GLEN SOUTH Cum. Cum. Cmn. Pressure Influx Press11Te lnfiux Pressure Influx A. Current Condz-tions ...... _...... 2,259 -4.7 2,269 39.4 2,058 36.3 B. Crintbzued Weslerose Injection to 12-31-76 ...... : ... 2.134 -9.2 2,162 38.8 1,730 72.3 c. Conditiolls at 12-31-76 with No Further Wesferose Injection l. Alt Pools at Forecast Rates .... _...... _. -. 2,113 -5.9 2,154 36.4 1,730 72.0 2. All Oil Pools at 75% of Forecast Rates ...... - .. 2,139 -6.3 2,178 35.7 1,730 72.3 3. All Oil Pools at 125% of Forecast Rates ...... -- 2,088 -5.4 2,130 37.1 1,729 71.7 Downloaded from http://onepetro.org/JCPT/article-pdf/6/02/43/2166126/petsoc-67-02-03.pdf by guest on 24 September 2021 4. Westerose at 10,000 Res. B/D ...... 2,114 -5.3 2,152 35.9 1,730 71.9 5. Westerose at 115% of Forecast Rate .... 2,108 -5.0 2,152 35.7 1,730 71.9 6. \Vesterose at 200% of Forecast Rate .. .. ··- 2,077 02 2,142 31.8 1,729 71.5 7. Bonnie Glen Shut-In...... --···· .. .. ·-- 2,178 -15 2,231 27.8 1,731 72.7 8_ ·westerose South Shut-In.. __ -··. ----. ... " . --- 2,139 -4.1 2,16! 38.6 2,Q42 26.2

CONCLUSIONS the forecast production of 4,600 STB/D. 9.-A '\Vesterose withdra\valrate equal to 115 per cent - -'·: L-The reservoir simulator is a satisfactory, conve­ of the forecast rate, over the next ten years, would nient and rapid means of predicting future pool tend to maintain the oil-water contact near its performance in the light of the past performance present level; a rate equal to 200 per cent of the of all the pools on a common aquifer. A mathema­ forecast would return the contact to the original tical model can be devised which will satisfactorily position. match past pressure perforrnaiice of the pools in the Acheson-Homeglen Rimbey D-3 reef trend. AcKNOWLEDGMENTs 2.-The results of the reservoir simulator should be considered as qualitative rather than quantitative, The authors wish to express their appreciation to particularly the water influx or efflux volumes. the British American Oil Company Limited for per­ The results should be considered as a trend or di­ mission to publish this paper, and to :Mr. D. L. Bow­ rection, rather than exact values. man and Dr. H. S. Price for their contributions to the 3.-The pools south of the Wizard Lake D-3 Pool ap­ studies. pear to be in poor pressure communication with the Wizard Lake Pool and the pools to the north. 4.-The \o\resterose and Bonnie Glen D-3 pools are in­ dicated to be in excellent pressure communication. The performance of the Westerose D-3 Pool is more sensitive to Bonnie Glen withdrawals than to Westerose South withdrawals. 5.-An efflux of 4. 7 million barrels of reservoir oil has .-,.··· D-3 occurred from the Westerose Pool into the <"f_ .-~ underlying aquifer, due to pressure differentials in ··: that aquifer. -•.• --., .=~: --- 6.-\Vith continued re-injection of produced solution gas into the Westerose D-3 Pool, the cumulative J. HNATIUK J. W. MARTINELLI reservoir oil efflux, after the next ten years, would be 9.2 million barrels. John Hnotiuk is reservoir engineer for the British American 7.-An efflux of oil from the '\Vesterose Pool will con­ Oil Company Limited in Calgary. A native Alberton, he grad­ uated from the University of Oklahoma with a B.Sc. in petro­ tinue, in spite of the termination of gas injection. leum engineering. Mr. Hnotiuk has worked in reservoir engi­ The cumulative efflux after the next ten years, neering with British American in Calgary since graduation. By however, will be reduced to 5.9 million barrels. coincidence, he started his career with that company as a '\Vithdrawals of limited volumes of gas from the switcher in 1952, producing the discovery well in the Weste­ . ~- '\Vesterose D-B Pool may be necessary if an efflux rose D-3 Pool, the subject of this paper. of oil from the pool continues as predicted. J. W_ Martinelli is senior project engineer in the Reservoir 8.-A constant withdrawal rate of approximately 10,- Engineering Applications Section of Gulf Research & Develop­ m~nt Company. He received a B.Sc. degree in petroleum en­ 000 reservoir barrels per day would be required to gineering from the University of Pittsburgh in 1958, and - ~-· maintain the current oil-water interface in the spent four years with Mobil Oil Company of Venezuela in Westerose Pool. This would currently require a various phases of reservoir engineering before joining Gulf. gas cap withdrawal of 3.2 :MMcf/D in addition to

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Technology, April-June, 1967, Montreal 49