. 4%?8

The Role of Technical Publications inThe Advancement of Fluid InjectionProcesses for Oil RecoveryMichael Prats, SPE-AIME,ShellDevelopmentCo.W. C. Miller, SPE-AIME,SheiiDevelopmentCo.

IntroductionThe upsurge [J reservoir engineering activity can beassociated with the year that the U. S. became a netimporter of crude oil: 1948. The competition of rela-tively low cost foreign oil, together with the risingcost of finding and developing new reserves, led in-dustry to increase its research and field efforts toimprove recovery from existing fields. Although theseforces still play a role, an awareness of the cominghydrocarbon shortage has been a more domirlantforce in recent years,.not only in improving recoveryefficiencies but also in obtaining fluid fuels fromorgb.]ic solids such as oil shale and coal.

The realization that the operator can markedlyinfluence the recovery from a fiekt by injecting fluidssuch as water da~s from the last century. Much ofthe fundamental work related to reservoir engineer-ing was available before 1948. Porosity, capillarity,heterogeneity, gravity effects, permeability, relativepermeability, mobi!iiy ratios, multiphase flow, PVTproperties of fluids (including retrograde character-istics), and the fundamental material balances de-scribing multiphase flow, were concepts well devel-oped by the pioneers in reservoir engineering (seeMuskat”’). However, there remained the tremendoustask of applying that knowledge to a large variety offield problems. This required an increased knowledgeand understanding of recognized concepts and dis-placement mechanisms, and the development of newones, through laboratory and field testing. It is thus

not surprising that in the decade following WorldWar 11 there was a marked increase in productionresearch facilities in the U. S.

In this paper we shall first trace the developmentand application of the various fluid injection recoveryprocesses since the inception of the Journal oj Pe-troluem Technology in 1949. We shall then assessthe role played by the technical publications of theSociety by studying the references cited. Although wehave selected those references that we think havebeen major contributions, our selectiofi has been in-fluenced by the degree to which they illustrate cer-tain points. We apologize for any major omissions.

In tracing the growth of fluid injection processes,we shall first discuss the recognition and apprecia-tion of factors controlling unrecovered oil.

What Determines Unrecovered Oil?Unrecovered oil may be left within individual pores,within clusters of pores containing relatively moreoil than adjacent portions of the formation, and inbypassed volumes of the reservoir. The factors con-trolling the amount of the unrecovered oil are oftendifferent in each of these three cases. To focus onany one of these cases, experimental equipment mg$~be”properly designed and operated.

When the unrecovered oil within pores is discon-nected, it is trapped by capilla~ forces. This oil iscalled residual oil, The capilla~ forces, which in gen-

DECEMBE%1973 1361

“A science which fails to give practical workers a clear perspective, the power oj findingtheir bearings and confidence that they can achieve practical aims, does not deserve tobe called a science.”- Trofim Lysenko

ml correspond to pressuredfierences across thecurved interface between two immiscible liquids, arein turn affected by the iaterfacial tension of theliquids, the curvature of their interface, and the wet-tabtity of the pore surface. Because capillary forcescontrol residual oil saturation, the prime target of themore sophisticated recove~ processes is to eliminatethese forces.

For a given rock, there is currently no exact pro-cedure for pre&cting the residual oil saturationresulting from an immiscible drive. Early efforts con-sisted simply of watertkoding cores to a very highwater cut, at which point the residual oil was deter-mined by extraction. Such procedures are basicallystill used today, but the diverse factors affectingresidual oil (or ultimate recovery) are taken intoconsideration by experimentalists who are careful.See, for exampie, Holmgren and Morse53 for theirinvestigation of the effect of initial gas saturation onresidual oil; Pickell et al.~’ for a study on the effect”of initial oil saturation and for a description of capil-lary trapping mechanisms; Moore and Slobod” forstudies on the effect of flow rates and interracialforces on residual oil saturation; and Richardson etaLMOfor their recognition of the importance of agingeffects on reservoir core samples.

Unrecovered oil resulting from the bypassing ofclusters of pores by an advancing flood front appeamto have been first documented by Chatenever andCalhoun.” This bypassing, as shown experimentallyby van Meurs,“ results from viscous fingering andcapillary trapping even in laboratory “homogeneous”packs, and is more pronounced the higher the oil/water viscosity ratio. Small-scale heterogeneities werethen shown by Dupuy et aL32to increase this bypass-ing phenomenon even for water and oils having thesame mobility.

On a much larger scale, unrecovered oil resultswhen regions remain unflooded at the time the floodis terminated. This gross bypassing determines sweepefficiency,which is affected by the mobility ratio, oil-bank buildup, and channeling through noncommuni-cating layers (Craig ef al.,23 Prats et al.i’); by buoyant

200NET EXPORTS

o

206 - NET IMPORTS

400 -

600 -

800 -

1000 -

1200 -1 I

1945 1950 1955 1960

Fig. l—U. S. petroleum exports and Imports (1945-3%5).

1362

OIL OIL

t t

WATER WATER

0 WATER E23 OIL

.

oiL

.t

WATER

= ROCK

Fig. 2-Oil trapped in a single pore.=

Fig. 3-Oil trapped in a duster d pores.”

PERIOD I

OIL BANKINTERFERENCE

PERIOD 2

01 L 6REAKTMROUGN

PERIOD S

WATER PRODUCTION

(sWATER BAN K

o OtL 6ANK

Q‘“ GAS REGION

X INJECTION WELL

o PRODUCTION WELL

PI& 4-Development of bypassed 011.’4

JOURNALOF PETROLEUMTECHNOLOGY

and capillaw forces (Craig et a/.,24Carpenter et Ul,’z);by ope}atio~al procedure; (Prats et ul~,ibKunkel andBarley’’”);and by nonuniformities in reservoir prop-erties, Although the examples given above are all forwaterflood, the same factors, with the exception ofcapillarity, affect sweep efficiency in all miscible andimmiscible fluid injection processes.

What Can We Do About the Remaining Oil?Wells are the access to the hydrocarbon accumula-tions, The O~~dtOr has at his control only the loca-tion, completion, and operation of those wells,

If he knows what factors control the amount anddistribu~ion of the oil remaining in a formation, theoperator can consider various ways to improve pro-duction. These may range from merely increasing thestrokes on a pump jack to installing a multimillion-dol!ar fluid injection system.

There is no assurance that fluid injection will suc-ceed in any one reservoir. But for any set of reservoirconditions, there are some processes that are more!ikely to succeed than others. For example, a thermalprocess, rather than a plain waterflood, would bepreferred for a reservoir containing a very viscousoil. If the sand is lenticular, so that communicationbetween wells is poor or nonexistent, a steam soakrather than a steam drive may be appropriate.

Decisions regarding the type of fluid injectionprocess to be implemented may be aided with res-ervoir studies. These range from simple desk-topestimates (Welge,”fiDietz,” Richardson and Black-well”), to very sophisticated scaled physical models(Gaucher and Lindley,’” van Daalen and van Dom-selaar,{”Claridge’O),or numerical studies (Todd andLongstaff,’:’ Thomas and Driscoll,’R Higgins andLcightcm4’).The model and numerical studies usuallyconsider a variety of operational options, such as welllocations and completion intervals, and injectionrates, in order to establish the best of several alterna-tive courses of action.

To avoid surprises during the course of a secondaryrecovery project, it is prudent and customary to firstpilot the operation in what is considered to be arepresentative part of the field. Since a pilot opera-tion is by definition relatively small, it cannot beexpected to behave like the full-scale project. Closeanalysis of the injectivity history will often providean early indication of an oil-bank buildup (Leppe2’),which may be corroborated later by a sustained in-crease in the oil production rate, The productionhistory of the pertinent fluids also provides clues tothe effectivenessof both the oil displacement processand bypassing behavior (see Helm’2 for an applica-tion to miscible floods). Asymmet~ in the responsefrom well to weil may indicate a preferred flow direc-tion within the reservoir (Lane61), a nonuniformityof initial fluid distribution within the pattern, or dif-ferent well productivities. These data should be usedcarefully in interpreting the progiess of the flood.Residual oil saturations and vertical sweep can bedetermined through the use of core holes (see Valle-roy et al.g’ for an application to a steam drive; Clarket aL’7 for an application to in-situ combustion). Re-sidual oil saturations in the neighborhood of injec-

DECEMBER,1973

tion wells may be obtained from special logs (Rich-ardson et al.i’) or through tracer tests (Tomichet al.~(’). In no pilot operation, however, will thecumulative oil produced per well be the same asthat of the full-scale operation (Rosenbaum andMatthews”), because oil will generally be displacedoutside the pilot area. Good agreement between pre-dicted and actual pilot response would lend credenceto the prediction for full scale (Craig”).

The Role of Field Case HistoriesA unique contribution of the JPT/SPEJ technicalliterature has been the comprehensive “field casehistories” that serve as a key link in translatingrecove~ process theory into profitable applications.The infinite variety of nature requires that we tailora recovery process to the particular reservoir beingstudied. On the other hand, useful (although by nomeans perfect) reservoir analogs can be found. Anunderstanding of their performance can be invalu-able in designing a new project. Nowhere is a closestudy of available field histories more essential thanin the application of the improved flooding processes.

Center

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(producerOff” center

odumr

I

5 layers w,lh

no Comunlcotlocl

between layers

Off cesler except et wellboreeproducer ~

jector

Center ‘+’;\/

prodUCel

Fig. 5--Grid blocks for representing an injection patternin a multilayer reservoir.w

!1 MAY, 1963 ;1

Soo’.

t

SCALEIN FEET w

Iw

Fig. 6-Block diagram of test site showing profiiesof burned reservoir.i’

1363

Characteristically, such processes involve injectingfluids — such as miscible solvents, chemicals, andhighly compressed gases — that are very expensive.

In the Society’s journals since 1948, we haveidentified some 200 of these field case histories;most of them arc concerned predominantly with fluidinjet on recovery processes. Statistics can give somegrasp of the tremendous variety and scope in thesestudies. In the U. S., the State of Texas (representedby more than 70 papers in the combined JPT/SpEJ)leads by a wide margin. Then follow California (25);Wyoming (14); Oklahoma (13); Louisiana and Kan-sas (9 each); Illinois (6); New Mexico, Mississippi,and Colorado (4 each); and Arkansas, Missouri,Nebraska, and Ohio with a couple each. The inter-national nature of the Society’s publication policy iswell illustrated by some 30 studies on fields out-side the U. S, Canada leads with 13; followed bySouth America (9); Middle East and Africa (4);and Europe (2).

The continuing importance of these field histonesto the novice reservoir engineer cannot be overem-phasized. They uniquely provide insight into and avivid introduction to the ast of anticipating themyriad problems that arise in the field. Any one ofthese problems may be fully capable of destroyingthe profitability of an entire field recovery project.

Gas Cycling of Condensate ReservoirsCondensate reservoirs proch-m high-API-gravity hy-drocarbon liquids, generally at high gas/oil ratios.The condensate may in fact have existed as a vaporat the initial reservoir pressure and temperature, con-densing as the reservoir pressure is reduced. Thisphenomenon is known as retrograde condensation.Condensate forms ooth in the reservoir and in thewellbore. The accumulation of liquid within thereservoir results both in the loss of valuable productand in reduced vapor flow rates (see Gondouin et al.42for a field study of the effect of condensate buildupnear the wells and Ham and Eilerts’a for a labora-tory experimental study). Recovery of valuable con-densate may be maximized by extracting the liquidsfrom the produced gas and then injecting the re-sultant “dry” gas back into the resemoir. This drygas injection helps to maintain the reservoir pressureat high levels, thus. reducing the amount of liquidscondensing in the reservoir. Furthermore, the dry gasalso revaporizes some cf the condensate present inthe reservoir (Cook et al.’”).

Stripping plants for recovering condensable fromproduced gas, and compressor plants for injecting thedry gas, are high-capital-cost items that can be justi-fied only if the economic incentives are high enough.The factors controlling the production behavior fromcondensate reservoirs became widely recognized inthe early 1930’s. S&e then, t;~e determination ofPVT properties, the predction of retrograde phasebehavior (Fatley et aL35),the determination of sweepefficiency, experimental studies on revaporizationphenomena (Smith and Yarborough”), and the cal-culation of interphase mass tmnskr during cycling(Rice and Donohue77) have become important as-pects of gas cycling technology. Buoyant forces tend

P1364

to separate the liquid and gas phases in the reservoir.And, in fact, such separation — even between theoriginal wet gas and the lighter injected gas — canbe important. Yet we are still not aware of any lab-oratory or field study aimed at quantitatively deter-mining how dry gas overiay influences the recoveryprocess.

With regard to field studies, Field et al.se have de-scribed in detail the use of areal numerical simula-tion in planning a large-scale cycling operation in adolomitized reef underlain by bottom water. In theirstudy they considered the distribution of aquifer andreservoir porosity, permeability, and thickness; thePVT and revaporization properties of the crude; thestrength of the aquifer; water coning; and cycling rate.

WaterfioodingThe main efforts in waterflooding have been aimedat improving the volumetric sweep efficiencythroughproperly locating and completing wells, through con-trolling injection rates, and through improving theratio of the mobility of the displaced fluid to thatof the displacing fluid. An excellent discussion of thedevelopment of this displacement process is given byCraig” in the Society monograph titled The Reser-voir Engineering Aspects of Waterflooding.

Laboratory studies on the effects of wells and in-jection rates have already been discussed under oneaspect of “What Determines Unrecovered Oil?” Suc-cessful efforts at improving the performance of con-ventional waterfloods are typified by the papers ofWayham and McCaleb” and Kunkel and Bagley.”Wayham and McCaleb discuss!how additional dataon reservoir continuity were (1) needed after the floodwas started, (2) acquired with the help of a coringprogram, and (3) successfully used through changesin the injection locations to improve the flood re-sponse of the Elk City Madison Unit. Their problem

● P,,T,

, Te In

TEMPERATURE - T ~

Pi, T, - lt5iTlAL RESERVOIR PRESSURE, TEMPERATUREC - CRITICAL ●OINT . .

Ftg. 7-Phise diagram for”ga$ condensate.”

JOURNALOF PETROLEUMTECHNOLOGY

was formidable because the productive interval wasa limestone section more than 900 fi thick. Kunkeland Bagley &scribe (1) both the technical and eco-nomic importance of balancing the response of eachfive-spot pattern in the Means Queen reservoir; (2)the associated difficulties resulting from the largevariation in the pore volume, reserves, and spacingof each pattern; and (3) the unanticipated ditlicultiesinherent in the reservoir. What once was thought tobe a blanket sand now appears to be a series ofrelatively unconnected sand bodies with poor com-munication between them. These two field cases ex-emplify most of the efiorts at improving waterfkmdsexcept that of decreasing the mobtilty ratio in orderto reduce the oil bypassed as a result of heterogenei-ties and of large-scale (viscous) fingering,

In an unusual application, Jordan et al.” describwlthe solution of a large number of problems in a pres-sure maintenance operation in which sea water wasused to enhance water encroachment.

Reductions in the mobility of the injected waterhave been proposed through injection of a gas withthe water and more generally through the additionof chemicals (such as polymers) to the water. Onegas-aided process uses injection of carbon dioxideeither as a slug or dissolved in the water. The gasdissolves in the oil to swell it and reduce its viscosify,thus reducing both the mass of residual oil per unitvolume znd the mobility ratio (Beeson and Ortloff,gScott and Forester”).

Sandifords2 described the laboratory and fieldpotential of polymers dissolved in injected water.Gogarty’O found that the reduced mobility of thepolymer solution is due both to increased viscosityand to the reduction of the permeability throughmechanical entrapment and adsorption. Dawson andLant.z” then showed that the effective pore volumecontacted by polymers is smaller than the actuai,thus allowing polymer solutions to advance and dis-place oil at a faster rate than predictable on the basisof total porosity. This has been their interpretation

for the early breakthrough of polymer in a field case(Jones?’). Bondor et uL”developed a numerical simu-lator that considers the polymer as a fourth compo-nent included in the aquemus phase, and used thesirrndator to illustrate two types of field applications;this model currently offers the most advanced meansof predicting the results of polymer floodh.tg.

Gas InjectionGas injectic,l is the oldest of the fluid injectionprocesses. It was first used because it was thoughtthat injecting water into rese~oirs could only resultin 10SSof production. Although it is now recognizedthat watertlooding obtains a better recovery efficiency‘becavseof its Icwer mobility ratio, gas injection isstiIl the preferred secondary recovery method in cer-tain circumstances.’e

Fields having established iow oil saturations ineither primary or secoudary gas caps are prime candi-dates for improved recovery by gas injection intothe gas cap. Gas injection reduces further shrinkageof oil and maintains a relatively high pressure gradi-ent on the oil phase; thus relative perrneability tooil remains high, and stock-tank oil is produced fasterand in greater q~antity. Under cetiain condition? ofgas cap drive (Richardson and Blackwell”), gravitydrainage of oil can be highly eficient. In addition,some vaporization of the lighter components willresult (Jacoby and Berry,fi’McFarlane et al.~’).

The injection of gas into an oil reservoir havingan unusually large amount of dissolved gas and alarge shrinkage factor has been discussed by Bartonand Dykes,’ Leibrock et al.”’ analyze the predomi-nantly crestal injection of gas in the Cedar Lake fieldto maintain the reservoir pressure above the bub-ble point; this approach effectively delayed ad-verse shrinkage and relative permeability effects. Thecrestal injection of flue gas in a high-relief sour-crudereservoir, leading to enhanced gravity drainage, hasbeen discussed by Stewart et d.” Even a thin sandaveraging no more than 5.5 ft has been success-

*

W w

Ftg. &lk Ba;n Madl;n resemmir performance curves.”

DECEMBER,1973

N:20

POLYMER F1OOD

t 1 I 1 1 1

0 .2 .4 .6 .8 10 12PORE VOLUMES INJECTED

~g. =il recovery efficiency, Iineer model?

1365

A

#

A

~

sz- WER \ --”-~--i” ‘;a~. lt)-(%oss--lon showing gas/oil contact vs time,

Elk Basin Tenskep reservoir.”

Fig. n-Displacement front at breakthrough (M= 71 .5).*

WATERCONTINUOUS PHASE

(Solubihzed Oil)

@

Spherical

OilMlcelles

OILCONTINUOUS PHASE

(Solubihzed Water)

&)’ H20

&--

Flg. 12-Micellar strueturaa (after Gogarty and 7oseh4’).

1366

du~ to the high volatility of the crude (Dorsey andBWey31).

Miscible FloodingFrom the eariiest days in the search for methods toimprove oil recmvery, the prospect of “washing”porous media with a solvent hx. been irresistiblyattractive. But a question persistd: How could thisbe accomplished without incurring uneconomic lossesunderground? Then in the API’s Drilling and Produc-tion Pradces annual publications, a breakthrough wasreported by Whorton and Kiesehnickg7 and SIobodand Koch*’: the diseovety that high-pressure injectednatural gas of suitable composition could, startingfrom a state of immiscibility with the reservoir crude,be transformed to a desirably miscible solvent. Thiswas accomplished by interphase mass transfer ofintermediate petroleum components. Many fieldswere amenable to this process; those that were notwere ripe for the next development. In 1956, Kochand Slobo@’ and Hall and GeffeniGseparately dem-onstrated the advantages of injecting a relativelysmall amount of solvemt(termed a “slug” or “bank”)and then displacing it through the reservoir with aless expensive drivi~g agent. The integrity of such abank is subjeet to deterioration by longitudinal andtransveme mixing (dispersion). Methods of quantify-ing these dispersive effects were provided by Perkinsand Johnston. ‘z

Numerous field tests of these processes were begun,and in time were recorded in the SOeietvjournals. Todate, these field tests total about 30. Smaller andsmaller slugs were tried. Some disappointing resultswere clearly explained by laboratory studies (Black-well et al.,’ and Haberman43), which demonstratedboth the high microscopic displacement efficiency ofthe process and the severe instabilities caused by therelatively low viscosity of the solvent drive fluid.

At the same time that the causes for the deteriora-tion of miscible slugs were becoming understood,other authom were suggesting procedures to improveslug performance, Caudle and Dyes]* and Blackwellet aL6 proposed incorporating water injection into themiscible project operating policy. The benefits havebeen confirmed in numerous field case histories, suchasthe Fairway (Texas), field report by Lackland andHurford.GO

There has been a continuing search for suitablemiscible fluids. The use of carbon dioxide as a solventwas proposed by Helm.’l That paper provided partof the impetus for the massive injeetion project begunin early 1972 in the SACROC Unit, Kelly-Snyderfiel~ in West Texas.

Surfactant FloodingCertain surfaetiint formulations can nxiuce interfaeialforces and thus displace or entrain and thereby re-eover oil that is totally unrecoverable by waterflood-ing. The major unanswered question is this: Can aprocess be devised that is elliciert enough to produceoil at a profit? A study of the JPT suggests that for-mtdations containing petroleum sulfonates may vetywell form the basis for processes capable of returning

JOURNALOF PETROLEUMTECHNOLOGY

.

an acceptable profit, Technically sound formulationsusing petroleum sulfonates in oil-continuous systems(Gogarty and Tosch”) have been field tested withencouraging results. Similar petroleum sulfonatesformulatd in water-continuous systems (Knight andBaer,37Hill et al.,’” and Foster”) have also been fieldtested. The test results have both confirmed the tech-nical feasibility of mobilizing oil in this manner andclearly indicated some remaining problem areas.

Direct field data related to the most importantfactors of these complicated fluid injection processeshave been disseminated through these references andthrough other Society publications. For example, sev-eral authors present evidence of the mitical require-ment for adequate mobility control in each successivestage of the process. Each of these impatant fieldtests represents a substaritial investment of moneyand technical talent by a single company. The ad-vance of this and other new technology is great]yaccelerated by making applicable information avail-able to all through the SOciety”stechnical journals.Before 1968, much of the available information onsurfactant flooding had to be inferred from judici-ously selected patents, which are normally written ina language unsuited for describing technical details.In the past 5 years, however, there has been a markedand highly encouraging increase in the number andcompleteness of surfactant flooding disclosures in theSociety’sjouma!s.

Special mention and commendation are due theProducers’ Monthly (Published by the Bradford Dis-trict Pennsylvania 011 Producers Assn.) for its rolein disseminating pioneer work in surfactant fhmding.A major part of the laboratory research publishedbefore 1955 was conducted at Pennsylvania State U.(Calhoun et al.,” Preston and Calhoun,’e Ojeda etU1.,09and Paez et al.i”). These early investigationsidentified the important factors and significantly con-tributed toward delineating the key roles of inter-racial forces, viscous, forces, adsorption of surfac-tants, and chromatographic transport of surfactantsin recovery by chemical processes.

Thermal RecoveryThere are vast deposits of very heavy oils and tarsthroughout the world. In our own country there isa concentration of such petroleum reservoirs in Cali-fornia. Because of the low mobility of the oil, recov-

eries and per well production rates are generally low.Even in the early stages of the oil industry, someoperatom recognized that heating very heavy crudeoil would enormously increase its mobility. This con-cept was combined with the knowledge that thegeometry of flow causm much of the available driv-ing pressure to be expended near the wellbore. Con-sequently, the earlier attempts were directed at heat-ing ths producing perforations (which often wempartially b!ocked by paraffin or asphaltene deposits)and nearby formation. Schild’a contributed a valuabletheoretical paper defining the benefits and limitationsof such wellbore heaters.

Subsequently, steam injecdon was recognized tobe a very effective method to introduce large quan-tities of heat into the reservoir. Cyclic steam injee-

DECEMBER,1973

tion, also known us steam soaks and huff-and-puff,allows the operator to produce unexpectedly largevolumes of stimulated oil even when steam has beeninjected for only a few weeks. Informative examplesof the use of this technique in California fields werepresented by Long”’ for the giant Kern RNer field,and by Adams and Khan’ for Huntington Beach.De Haan and van Lookeren” and Bowman and Gil-bert’ described spectacular results under Venezuelanconditions. Among the many accompanying theoreti-cal descriptions were those by Boberg and Lantz,7Closmann et al.,” and Niko and Troost.” Their re-sults agreed with observed performance and showedthat the natural drive mechanism is a key factor inthe stimulated response.

The main elements of continuous steam injection,as a displacement process in the manner of water-flooding, were thoroughly analyzed in a landmarkpaper by Willman et al.” Again in this technical area,Society publications were the prime sources of eyc-opening results from field projects throughout theworld: from Venezuela (de Haan and Schenk2’i),fromThe Netherlands (van Dijk’3), from Texas (Halland BowmanJ’;),and from California (Blcvins et al.,’;’and Bursell’”).

The relatively high cost of the injected fluid (about20@per barrel of water to soften and heat from liquidto steam) requires careful and imaginative projectdesign. Marx and Langenheim’4 and later workersprovided simple methods for calculating the si.zcofthe heated zone created by injecting the hot fluid into

——

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-——_

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Fig. 13—Primary production and steam-soak productionfrom repeated cycles.a

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~. ‘14-How diasn’am of tast.=

the reservoir. Mathematical simulation — modelinpthe physics of both hot water and steam flow —promises to be a most useful tool for this purpose.

Injecting air into petroleum reservoirs generatesa series of potentially useful reactions — for example,generating heat diiectly in the resrxvoir and creatingsteam as part of the oil is burned. One of the earliestJPT papers on this subject (Grant and Szasz”) em-phasized an inherent advantage in this method“sensible heat of the rock behind the wave (the hightemperature zone) would be continually recoveredand uti!ixd to help heat ‘new’ rock ahead of thewave.” A continuing stream of technical papers (aver-aging some four per year) has followed. Of these,the paper by Wilson et aloe introduced the conceptof sequential oil and steam zones, and that by Gott-fried” showed how to solve numerically the three.phase flow and energy equations to calculate the pro-duction history of a linear system. In 1958, at arelatively early stage, Gates and Rameys8 dLc.medin meful detail the field test in the South Belrit.ge(Calif.) field, The subsequent literature alerted petro-leum engineers to the proper procedures, possiblepitfalls, and further technical advances (such as com-plementing the injected air with considerable volumesof water). Outstanding papers that come to mind onthese three subjects are those by Casey,’S by Earl-ougher et al.,”” and Dietz and WeijdemasOand Par-rish and Craig.’]

The growth of thermal recovery in California pro-vides an unusually clear illustration of the impact oftechnology upon oil production. Over a period of afew years, in a relatively small geographical area,production rates from old fields have risen sharplyand new accumulations have been economically de-veloped as &result of a combination of steam stimu-lation, steam drive, and in-situ combustion. Cur-rently, at least 140,000 B/D, or 15 percent of Cali-fornia’s production may be attributed to these recov-ery processes.

ConclusionsItbecame very obvious during the preparation of thispaper — although there is not space enough to elabo-rate upon the fact — that there has been a tremen-

Fig. 15-Schematic drawing of COFCAW saturation andtamperatura profitae.”

1368

dous amount of interplay between those who itnple-ment commercial fluid injection operations and thosewho invent, develop, and improve the processes. Infact, there are numerous cases h which certain indi-viduals have been leaders in both activities at varioustimes in their careers. It is also quite clear that thisinterplay has required an equally extensive feedbackof information in all directions and at all levels. Thepublications of the Society have played a truly keyrole in this exchange. When unusual behavior hasbeen noticed in a prmluction operation, it often hasprompted some explanation, which, :n turn, has re-quired experimental or theoretical corroboration. Theother side of the coin has also appeared: a techniquefor improving performance is first postulated, thenit is tested in the laboratory and later in the fieldbefore it finally blossoms into an accepted commer-cial process. These patterns repeat themselves, some-times in both dkections, throughout the developmentof each fluid injection process.

In this regard, the preprints of papers presentedat Society meetings must be given credit for dissemi-nating much of the detailed technical informationeven before the papers are pub:lshed in final form.These preprints help foster the free exchange of ideasand results when the papers are being presented. Theincreasing spirit of candidly disclosing significanttechnology early in its development — a spirit re-flected in the goal of the 1972 ‘I’uIsaSymposium onImproved Oil Recovery — is one of the most encour-aging signs in the industry’s tight to meet the world’senergy needs.

As indicated by the references cited here, most ofthe significant papers published since 1948 have ap-pearqd in JPT and SPEJ. These publications are ina sense living memorials of the development of newand better secondary and tertiary recovery processes,often from a mere idea to large-scale profitable fieldprojects. During the preparation of this paper, it wasa pleasant surprise to notice the high shelf life, vi-tality, permanence, and pertinence of many of thepublished papers, even those dating from the earlyyears of the JPT. In addition, the scope and compre-hensiveness of the publications related to subsurfacefluid injection processes, and the high frequency with

t

which the Society journals are cit as referencesthroughout the world, are a convi ing demonstra-tion of the outstanding position eld by JPT andSPEJ in this phase of reservoir engineering.

The period of maturity of the more sophisticatedfluid injection processes is still to come. Subsurfacerecovery of fuel products from tar sands, coal, andoil shales MI lies ahead, as well as the widespreadrecovery of energy from thermal areas. The tech-nology is getting more complicated, but higher in-centives resulting from an increasingly serious energysupply/demand position will force attempts to de-velop these relatively untouched areas. Even thoughcompetition will be much greater in the next quarter@ntury as technologists in other disciplines becomeincreasingly involved in solving the problems of ourwidening industry, the journals of the =tety of Pe-troleum Engineers of AIME will certainly share inthe coming growth.

JOURNALOF PETROLEUM TECHNOLOGY

53. Holsn~ss, C. R.<and Morse, R. A.: “Effect of Free GasSaturatmts on 0s1 Rexovery by Waterfiomling,” Trans.,AJME (1951) 192, 135-14??.

54. Jacoby, R. H. and BSmy, V. Jo, Jr.: “A Method forPredicliag pressure Mainteaaace Performance for Res-ervoir Producistc Volatik Cwie OiL” I’runs.. AIME(19s6} 21% i9a. -

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This is psp& WE 4698 @ Copyright 1973 American Instltutsof Mini- Mstsllurgieal, snd Pshtsum Eqinssrs, he.