Secondary and Tertiary Methods in Soviet Oil Production
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Soviet oil pfeduction it encountering interrelated problems in exploration, drilling, production, field processing, and Iransponaiion. Crude oiloperations arc concentrated in West Siberia's Tyumen' oblast. which3 wasuotaercent ofillion tons planned for the USSRhole. Ai one point. Tyumen' produclion reached the record rateillion tons per day, but the industry could not maintain it, and the totalJillion tons.
The .Soviets may no lonicr be able lo cope with their mounting production problemsne-third of the Tyumen' wells were reaching the end ofproducing life, and drillers were pulling into operation only Half as many new wells as would be needed to replace ihc'm. Reporting often mentions idle wells, as well as inefficiency in well operation due to lack of maintenance.
The Soviet press has commented that, wilh Tyumen's inadequateany weak link in produclion. processing, or tiansportaiion weaken' the cnlire operation. This paper discusses one of ihose links- ihe industry's trouble in applying secondary and iciiiary oilime when declining well flows and rising water-cuts call for iheir more intensive application.
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Secondary and Tertiary Methods in Soviet Oil Production
t tkii itfiO'i
t
application of secondary and tertiary methods of oi! production is becoming increasingly critical to sustaining oil outputigh level in primary production, the flow of oil depends on natural reservoir pressure, which drops as oil is removed. Secondary methods fwaicrflooding. artificial lift) and tertiary methods (flooding with steam or chemicals) can prolong the flow. They demand substantially more investment, manpower, and technology than natural well flow but piomise higher oil recovery
production method* arc widely used in the USSR. Watctto maintain pressureell is initiated soon after the onset of primary production; as larger volumes of water are injected into the oil reservoir, more artificial-lift equipment (pumps and gas lift) is required lo stabilize Ihe flow of oil.5 loercent of total Soviet oil Output came from fields that had been water flood er*
In the new areas being developed, the reservoirs arc likely to be smaller and well-flow rales lower lhan at currently operating fields; the application of secondary production methods will be cosily in investment, labor, and maintenancelan calls for the number of oil wells on artificial lift to increase by more thanercent. To produceillion tons of oil plannedhe Soviets mustillion tons.of fluid (oilercent moie than0 Moreillion ions of this would be lifted by pumps.5 thefor artificial lift will be even greater
Soviet industry probably will not be able to satisfy these massive need* During the past several years, il has failed to meet its goals for artificial-lid equipment byoercent annually Moreover, the domestic equipment is poorer in quality lhan that available in the We*.'. US-made cJcciiic submersible pumps have been important in Soviet sccor.dary recovery since, whennits were imported. The Soviets wish to buy more of these pumps, as well as spare parts, but USpolicy has hail the effect of delaying purchase
Equipment shortages contiibute to the wells' increasing downtime for mechanical repairs The magnitude of the maintenance task was illustratedhenell repairs weref which involved artificial-lift equipment. By ibehe oilfields could regime moreepairs amu"Hy. and an even greater share Could involve artifirial-lili equipment
In one plan for, the Soviets calculated that ihe use of Western equipment in secondary recovery would provide significant savings.{unrealisticaUy) to put0 oil wells on gas liftells on new hydraulic pumps. they estimated lhat by using Western equipment they could do Ihe job with thousands fewer pumps and workover rigs,illion well repairs over the decade, and cut their maintenance force0 workers. The combined savings wereatillion rubles
In recent years the USSR hasrogram of tertiary production methods to recover more oil from old rraervoiis. but the commercial rcsulls have been insignificant.1 the Soviets obtained onlyillion tons of oil from these enhanced oil recovery (EOR) techniques, orerceni of total Soviet oil produclton. They appear io have conducted laboratory and pilot tests on almost all of the EOR processes known in the West, but commercial application ii hampered by shortages of equipment, chemicals, and trained personnel
Published plans call for EOR to yield oil output ofillion tons5 andillion tonshese plans appear to be extremely ambitious, in view of the limited domestic capacity to supply Ihe equipment. The Soviet Union currently depends on Western assistance in these complex and costly operations. Even if they give EOR an all-out priority, we doubt that the Soviets could mcei ihese goals We estimate that oil production from EOR methods could reachillion tons5 and no more lhanillion tons0
In the West, the slack market (or etude oil has slowed the use of EOR, which not only is capital intensive but also requires long lepdtimes beftre oil is produced. Oil production by EOR melhods in the United States has remained nearly constantlthough some indicationsignificant rise in application of EOR techniques in the coming decade
Secondary and Tertiary Methods in Soiiel Oil Production
Tbe techrisquca for extracting crude oil (rem petro-teutn rcKTrctri are commonly classified a* prirnary. seceeiCary. and tertiary Primary prodDClMo entailseodoctioo well mioerode ail rearavoir. There oil. gas. and coeinalc water* arc trapped in ibe small porta of the reservui rodcaling layer of cap rock and are iub>eci lo considerable pressure from the overlying rock and from the hydro static force of the underlying around water. At thisarge share ol Ihe gai present in the reservoir is usually dissolved in the oil. Once the impermeable cap rack is |neiced by the drill, ihe compressed connate water, Ihe oil. and the gas in sotCtion expand and move into thecllbore and upward. As this natural reacrvuir energy declines, SO does the rate o' oil productionVowing -el'
To sustain pressure in the reservoir and to maintain oil flows at an efficient rateonger period, recondary production methods are normally initiated sooe afterset of natural production These methods involveedium into ibe oil reservoir (figure IH The medium is usually treated water or gas. depending on reservoir conditions.is mosl often employed early in the cycle of Soviet field development Over time this causes an increase in the water-cut (the proportion of water in the mixture of oil and water produced from an oilater is heavier than oil, and water cuts oferceni or mote necessitate the extensive use of artificial lift (pumping and gai lift) equipment to Stabilize tbe flow of oil as increasing volumes of waterbe produced together wiih the oi
Evenuccessful wairrflood. lubstaolislof oil remain in Ihe reservoir If it ia considered worthwhile, leniary productionserosal and/or chemical ircalmertt) may be employed to
Wninliui lognw la ihe Hwe toneiui aaii'il lim ('i- of uii'i HOuaOraca am-niwivoiiMpIum csfdirv aiinrtid
increase the oil recovery Still further (thoughower rate of output) by altering ihe natural fo-ees that hold tbe oil'tn-plBcc in the pores of the reservoir lock. Tertiary methods, usually referred to asoil recoveryre technically more complex and coosidei-bly more expensive thanmethods ofn addition, ihey themselves consume substantial amounts of encrgy-to generate heat for steam or to manufacture the necessary petroleum-based solvents and otherSoviet attempts to apply EOR have beenby tbe need:
Foe tailoring tbe EOR applications precisely to the local conditions at eachindeed, al each well.
For large amounts of geological data on the reservoir.
ree of specialiied etpertise on the part of technicians al the production site
Secondary Methodsaod Con
As natural reservoir pressure declines, the flow of oil slows and eventually stops However, both the oil-pioduction late and the amount of oil ultimately obtainedeposit can be increased by appiopri-ately engineered water flood pressure-maintenanceThe water flood process involves pumping water into the oil-bearing reservoir through wells drilled at its flanks and base to force 'he oil to flowtbe production wells.ule, water can raise reservoir pressure quickly because o( lis higherrelatively efficient displacement characteristics.
' ThecOwiv an -irisui If sinned vaeil isduiirt and legit unto Sewt*sr riAontW ramri ui ttm< cirreorynclude iU nf if* rokaiquoinnd imiary recovery; oitiersllH term as aifMntui for rMi'my rrMwronti We useall 'rcowrf (EOR) ia lie tiller rente and define ihi eifcer icrms
fa nett rmusito-tcl owJliw-.
andincompressible nature. By prolongingconomic liferoducing oil well. waterflooding can substantially reduce tbe requirement fur drilling and can bold down Ihe cosl of producing additional
ail " "
Waierladoding leaves behind significant amounit of Oil, however, for two reasons.s ihe water moves through the reservoir rock, il does no. Hush all the oil from the pore spaces. Because oil and water do not mix. oil is left behind in the form of droplets and pools held within tbe smaller pores; these can add up to more thanerceni or the oil originallyeservoir. This problem may be alleviated somewhat by the use of additives. Second, as the water "front" advances, i: tends to follow the larger channels and sometimes bypasses significant portions of thebecause of changing litbology or microgeological conditions. Thus, the waterflood may not sweep all areas as efficiently as planned and may leave much of the oil behinc'
Soviet Waterflood big Practices Since World War Ii, waterflooding has been cm-ployed in most new Soviet Cmfolds soon after the atari Of production and has raeen exxtunued throughout Ihe life of these fields. Watee-injected fields accounted for mole lhan half of the oil produced in the USSR as early5 and foroerceni7
By providing higher initial output per well than would be possible under natural drive alone, waterfloodins has enaWed the Soviets for more than two decades to minimise their initial oilfield invesiment by holding down the number or wells and pumps required
Although waterflooding results in high production rales in the early years of anife, it can produce complications;
- In some fields, tbe Soviets carried the practice to extremes, raising pressures beyond ihe original level enough to rupture Ihe reservoir scab and cap rock.
' ia rhc Uniiedrimary neural dn^ prrrf-irc .is
in it* (Stirw because of ibeo-fcirshlr. of oJfieJo" mcaerils ll lot* yean of negotiationmaforu. ofrr,iouai,hu, is
tesitireeoerations couldto die USSfi.
hmtxr. IKi- nunciah. tn ilxfr areinii.ir. In early -iter flood in
7 Ihis malpiactice waj reported ai many Volga-Urals fields and at several largencluding Samotlor.
Ideally, the injected water moves through Ibe oil-bearing formationroad front, from thewell to the producing well; however,finger" of water under pressure breaks through to ihe producing wells, tbe rest of the water will follow Ihis easier path. When this "coning- happens, addi-lional wells must be drilled (infill drilling) to locale the bypassed pockets of oil. and more of ihepumps or gas-lift equtpmeni must be installed.
The produciivity of artificial.lift equipment and Ibe maintenance burden associated with its use are often affected by unwanted consequences of waiernoodiog. In the Middle Ob' producing region o( West Siberia, for eaampse. the underground aquifers havevolumeupply all the region's water injection needs. Therefore, ibe Soviets added untreated surface water from lakes and rivers lo the aquifer water and recycled water. Untreated waier in some Sovietfood projects has created problems in ihe reservoirs:
recovery was reduced by the lowering of bottom-hole temperatures when cold surface water was injected into the highly para(finic Uxen-Zheiibay reservoirs or ibe Mangyshlak Peninsula. The same problem occuired at Samoilor and Ust'-Balyk in West Siberia
Injection of untreated water has led to excessive sail formations in well bores and dctwnbole pumping equipment at Samotlor and in West Siberian fields.
Oiganic material and dissolved gases in untreated surface waters injected into hot oil reservoiis have also caused prolific bacterial gret-ih. reducing rock permcabilily and porosity.
Many West Siberian res-jvoiit consist or sands and mcntmoiillonile days, which when flooded lend to swell and lower the formation's permeability and poiosii)
Seeiel
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Figure 2
USSR: Oil Well Fluid
Ailbocgh Ihe Soviet! plan lo employ Uric gat lift tyitems in tome keyhe ihaipiy riung fluid hd requirement! point to an orgeat near-termor many high-quality putnpt of appropriate tile to cope wilh incrcaung volume* of water aod oil. Tbe Soviet) have recentlyarge order for tubmcniblc pumps wilhUS firm (tec discussion in the section on pumping requirementt) '
Pumps can be insulted fatter and with lest capital coat lhan gat lift, but art more costly lo maintain and ara down more often for repairs. The impact on the oil industry of large-scale use of pumpi and the concern-mitant maintenance burden is already serious. On the basil of information from Soviet technical journals,stimate that at any oneoot one-third of West0 active well) are Hie because of equipmentound Samotlor, for example, pump breakdown* are occurring with increatingaverage lime between breakdowns hit decreased in recent yean from0 days to SO days
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Inert alias Rfqiarrrocnl!Artificial Ufl Wiih increasing numbers of new well* being dulled and old wclb "watering oni" rapidly beeaittcr funding, ibe Soviet ctl industry'* requirements for artificial Ufl of fluid will escaltte rapidly. In ability lo meet these requirements will be critical to oil-production ptcopccis during tbe remaindei ofhe burgeoning proportion of water in otl well field production it illedFigureany fieldi including tnrttl of Ihe largest andpatted their pome. Stabilization of oil ontpat (that it. in maintenancelanned level) at tbe luge field) will require conversioname number of flowing wellsll 'id operation (major type* ofequipment are ibown ia figure IX It will also require conlicoed development by infill drilling The increasing ekpetsderivC of nl output on dodopuvenl of numerout tmall new fieldian additional fai im bearing on ihe need for pumping equipment
Ihe importance of lubmcrsiblc pumps in Soviet oil prediction rt illustrated by production, data0 In thai year apptotirnaietyercent of the active wells in ihe USSR were exploited by submersible pumps, which accounted fot:
ercent of ibe total oil producedMore than half of the total fluid prodoerd
erccoi of the oil produced by artificial-lift methods
0 tbc USSR had importedigh-volume. US-made lubcncciible pumps with aannual capacity of1 'J million tons of f! md -enough to recoverercent of the oil produced by all tubmersible pump* in the USSR.
0 the USSRo imported Western gat-lift equipment foril wells; but0 Onlyoercent of'this equipment wst estimated toperation.0 the coinbincd capacity of the Western gas-lifi equipment in Soviet oilfields wet probably aroundillion lont of fluid per year, and it produced aboutillion toot
-Secret
re:
ii -ni nearly half of Ihe total amount produced by ill gas-lift eouipment, Soviet andonlyercent of total crude oil output In lhat year
Tbe rote of artificial lift is graxshacau'y illustrated by Ibe ejpertee.ee in the Volga-Urab fieldt00 Ihe average water-eni in tbe oilfieldi of IheSR rose fromercent io overercent. Thit meant that foe every ton of oilthe producers had toorn of water0ornnly special high-volumeequipment can cope with tuch Increases in theof fluid, and the equipment moil commonly chosen it the submersible pump
Impact of Aglrag
Al oil welts age. operating problems intensify After an initial five-even-year persod of rising rait prodiiettOA. fieldseriod ofchar-acteriicd by almost fiat, or stable, production; this laitt from five locari. Thereafter, outputdeclines loa point where production at lhat field is no longer economical
It is technically impossible io stabilise oil production for more than aboutears. During the yeats when ii is feasible, stabilization requires constant infusions of new capital, labor,er resources for new ifisullatsons ai ihe mature fields la addition to these ci peases, coo version of flowing wells to artificial Idi operation usually leadsharp rise in maintenance requirements due to bi cake-owns of pumps and gas lift equipment and lo well-casing leaks The magnitude of such conversion and maintenance requirements facing the Soviet oil industry is evident from the rapid increase in (heof fluid to be produced by artificial lift (figure 4
In Soviei practice, pumps are usually installed al the producing well once the water-cutercentell's total fluid output The volume ol fluid that must be lifted is of course, tabtiaaiaaUy increased when waiejIVoocfLsg is used. Nearly all of thehe USSR arc rtsorc thanean old. and2 the nationwide average water -cut was oveierceniasercentiendt in watei infection, fluid production, and water cut arc shown
Mayor Types ofOilfield Pumps
The rod-and-beam 'sucker-rod/ pumpi wedin oil welt serviceelatively primitiveylindrical working barrel attached to the lower end of tubing il suspended from iheInside theower-actuated walking beam at the surface raises and lowers (by meansolumn of "sinker"lunger set below the fluid level Inside the working barrel. Oil trapped by valves tn the working barrel is lifted through the tubing with each upward stroke
The electric centrifugal submersible pumps used in high-volume anificial-tift operations involve more sophisticated technology in both materials andTheir threeelectric motor, achamber,umpencased in seamless steel tubing with watertight< entire assembly is suspended in ihe well on tubing through which ihe fluid is pumped to the surface. Electric current is transmitted from the surface to the downhole pump motor by an armored cable clamped at intervals to ihe outside of the discharge tubing1
in table I.! the Tyumen* oilfields were cipcci-cd to produceillion tons of oilater-cut oferceni)illion tons were to coosc frommen lor. where the wjier-cwt is i* perceni and jxodoction is ia the early stage of dee line5 <be nationwide water -cut will approachercent
The one-year and five-year plant for oil irtduilty operations oughi ideally lo be geared to total fluidIs, the goal (or oil productioniven year contains an implicit assumption o( what ihe water cut will be in that year, and this assumption ought to be realistic Estimates of the volume of-tic-thai must be coped withiven year arc always sutooclariety of faesors Acbtevvrsg Ihe target lor oil production deperseh on there being enough pumps ol Ihe right life (or. (or some fields, gat-lift equipment! Buthe USSR ihe supply of equipment
Table I
USSR:egation, Fluid Production, and Wnrer-Oit
IOH
InreiM
uld
r oa
r.
[
jUn
ill plln
IWraaa
'a-
im.it
timait
W, ctlimale total fluid RroducUoeoaol -ato-eut dala and plans recoiled In St-lel puabcaiiuni.
New: firsroioo- actuali-.h. IIriSf uan
-tatitO. p'x. mmonet produetion atus. aad
irdKaiuCIA tmm.i-
to stabilize crude oilThe document catimaled that at leastubmersible0 fas-lift units,0 morem pump units would be lequired over0
Production of such pumps liaiied far behind (he need, and the effect of the shortage is evident ina list ics on oil production by primary (natural flow) and secondary medbods. Foroviet oil iodustiy journal reported that9 onlyercent o( oil production came from wells on artificial lift, instead of theercent or SO thai had been planned.rtificial lift probably accounted (or no more lhanerceni of oil output. This means that oil
It is note-ortll, ibat in WO it* So-let ttenocrih.i
crude Ol rnoductkwrcmiia fltiem
VisIter irrcoectioru Urn ths
.vesecerot* it IMSit roam by IM0 Toialproduction isetodc. rm.ll ammessol crude oil cod onion by IhrMiniiiry. ascndcnuie
Ironi antral an producec output by natural flow from old watered-out wells and from newly drilled infill wells, even though it was declining, still accountedreater share of total production lhan had beenercent instead of the plannederceni) because of the lack of pumping equipment (or artificial lift
Between8 andhe planners revised sharply upward their estimates of lotal fluid (Oil plus water)outputS, fromillion tonsillion tons. This calledefty increaseecordillion tonsf theillion tonsiim commitment, the plans for pump production5 would also have had to be revised sharply upward If pump production is rising as the plans require, these trends suggest lhat tout fluid output couldillion tonsf
The water-cut is rising faster lhan ihe Soviets had cipcctcd We anticipate that the nationwide average water-cui will .rwrease fiomerceni0 to
aboutercent inabove tbeercent earlief projected oy Soviet planners. Oor estimate takes into accountpcrceni nationwide water-oil reported2 and ibe Soviet rejectionspercent waiea-cui in Tyumen'pcrcent water-cut ai Snmotlor?
The substantial impact ofercent change in waler-cut on tola! (luid-liri reeniirements may be illuttraied by reference lo the Soviet oil induitry't etpeitencet thown in tablef the average water-cut had beenercent.riginally planned,illion tons of oil output would haveotal fluid productionillion toot Withpeicem waler-cut in ihe revised plan, however, the implied production of total fluid for the year amountedillionercenl change in water cut implies the lifiing of an additionalillion tont of fluid
Pumping Reo air emeu isnn an article discussing requirements for Ihe coming decade, the Oil Minister stated Ihat50 onlyerceni of the active wells are espected io flow (cither with natural reservoiror with pressure maintenance from water or gathis low proportion of flowing wells,with the rapidly rising water-cut.iemendous need for more and boiler pumps of the proper capacity if the Soviets are toecline in total oil prediction in Ihe. The sharp increases in requirement! for aitificial-lifl equipment estimated50 arc illustrated in figure 5
-Seere t_
Figure 5
USSR: Utilization ol^rtlficial Lift, by Type
Ihe Soviets expected water cut in ihe Tyumen' fields j< Wat Siberia to rraehercentittc omvertioo of0 flowing welts IO pumps should beorider way The limine and rale of decline of ibe older fieldsyumen* will ool be easy to offsetoderate by infill drilling because new-well piodoctiviiies there are declining. Thus, artificial lid willajor factor determining West Siberian ui prcdwcltoa Nearly two-thirds of the wells on artificial bfl in West Siberia arc already erjsipped with submersible pumps, accordingoviet oil industry journal
To meet their current crude otl production planahe Soviets have alienated that ihey must cope withv> percea: increase in total (noductno of fluid foil androm oil wellslanned increase fromill ion tons0 toillion ions. The task will call forthe number ol producing wells on artificial lift0 toithin five years. They expectchieve much of theement in oil production from wells on artificial lifl by equipping0 more oil wells wiih submersible pumpsore with gas lift.
g. growth in Soviei oil production has slower)ritical need for large amounts of Western fluid-lift technology and equipment already exists This need should intensify ai moie of the giant and supcrgiant fields age, become depleted, and begin to produce nostly water. If adequatelift equipment is not made available, Soviet oil output will almost certainly decline sooner and morefc; oil-production history of the Talar ASSR provides an example of the requirement for artificial lift ai water-csm increase. Tatar oil product ionaai-mumillion ionshen ihe average water-cut foe the region passedercent.0 the waier-CUf decodedercent,ercent of the0 active wells were on artificial lift, and submersible rumpserceasl of ibe ml million tons of oil recovered
In4 the USSR took initial Kips to obtain better pump* from the Weal,ontractS firm for tbe saleigh performance iltmetsible pumps valuedeirannual capacity will beO million ions of fluid Delivery and installation ofumps will probably take IS months and come too lale to have much impact on Soviet oil output in the current five-year plan Tbese pumps will, however, help stem decline inh plan Follow-on orders may be included in future Soviet plan'
We believeailure to meet ibe massive needs for artificial lifi equipment (which could urns in pan from eonstrainis on inveatmeni and ntanpowerwouldowerful force for decline in Soviet oil prndueiion in theiih respect 10
ll alone, equipment supply in iteenifar less ambitious programs than will be railed for in (he second half of the(railed demand by aboutoerceni annually
Equipment and Maintenance Rcqulrcntntk The USSR's oil output targets imply the needharp increase in the supply of artificial lift equip-mcnl. As water-cuts climb, so do the requirements for high-volume submersible pumps Providing them willurdensome task for an economic system thaiould supply no more lhanercent of the oil industry's pumping needs. It also implies aadditional task of providing the inercatc in manpower and industrial supplies necessary formaintenance tasks. Both will be difficult to achieve
Soviet industry has made Utile progress in developing improved high-volume pumps since the need for these items was first :ccogmtcd inlant was activated at Al'md'ycvskul in2 its serial production of these pumps still failed to meet standards for quality and quantity. The Soviets have made some advances by using their cuttingmore efficiently, bul significant technological breakthroughs cannot be capectcd0 unless they improve their capabilities in metallurgy and precision manufacturing
Soviet plans for development cf new oil reserves deal with deposits much smallet in site than the giant fieow being eaploited. Thinner reservoirs and, in some cases, higher viscosity crude oil will certainly lower the well prodoctivilies and increase the need for artificaSI lift. Tbe heavier crude oil. in addition lo being more difficult to pump, usually contains more corrosives and contaminants. The incicase in average viscosity, comingime when the Soviets will haveumpons of water for each ton of oil.gicatly complicate their artificial-lift operation*/
Bothmore active oil wclb and much moie artificial-liftcreate ain well-maintenance services.ell-repair jobs {woikovert) weie performed in Ibc oil industry, langing in difficulty from cleaning ihe wellboie through repairing the casing and pumps to rcpcrforaling lhc casinget mil freer flow of oil into tbe wcllborcf these repair jobs involved artific-iMift equipment submeisiblt pumps, gat-liftd rod-and-beamrhat require pulling the equipment op lo the surface occur three to four times at often in ibe USSR ai in Ihe United States, jcerxding to Soviet data
The magnitude of the maintenance task it highlighted by the following Soviet forecast of Ihe approximate number of oil welts that would have to be equipped with artificial Ufl10 under the produc-lion assumptions (in number of oil welli) underlying the estimates shown in table 2.
EleeUie lubmcatiWt0
Gas-liltVM
Rot-nnd-hKU
Unless marked improvements in Soviet equipment and technology reduce the time between repairs, the requirement for well-repair jobs in theouldear
r*ai I'ampi Soviet rod andpumps have an average lervice life ofaysrepair* (in the United States the equivalentays) Most mechanical breakdowns are caused by: (I) breakage of pump rods (currently,0 per year because of their haw tcruileoot tleeve bearings, and (J) sleeve misalignments. Soviet oil wells using thit type of pump are deeper on average lhan those in the Unitedactor contributing to the relatively greater incidence of pump-tod failure-
For nploting high-volume wells, rod-artd-bcam pumps are less efficient than submersible pumps and gas-lift equipmen
.Increased use of high-qualiiy. high-volume submersible pumps from lhc Uniteddale the only provensubstantially Soviet manpower and maintenance
requirements (or Oilfield operations and probably per-mil higher oil output. Soviet ind US elective lubmcrs-ible pumps are of Ihe lime general design, indeed. Soviet design Standardi arc bated on publiihed US pump specifications. However, the lack of appiopriate metallurgy and machining prevent! Soviei pumpr from matching US standards (or fluid output and service lit.
Submersible pun<ra> have been inttallcd at one lime or another in mott oilfieldt wiih highprod net ml yRomathkiao. ledorovo. Artta. Ne Oil Dag. Uieri-Zbeiibay. and maay other VetgaUrah and West Siberian dccnsiti Depending on pump tiie
and veil conditions. US units ranons of fluid per day. Soviet pwmpi average lessons ol fluid daily, withew uniti lifting moreorn (SemeI prototype unitson-per-day capacity are being tested I
The Soviets havemany years of experience in (he same oilfields with domesticpumps and with US Reda (TltW|fc 'i1 ion)the US pumps art about twice aa elfkseni as (heir own Breakdowns are fewet and average seivice life isdays between major overhauls for US imports anddays (or Sovietme of ihe more corrosion resistant metals and the (ar greater precision used in ihe manufacture of US unit)
Moreovet. for pumps immersed in hoi. corrosive fluids, the Western-made elect iKpo- ei cable is much better lhan Sovsel cable The cost of any cableis purpose is high (usually eaceeding the costump at depths greaterut the cilia original coal of Western cable can provide overall economies by reducing the incidence of short circuits and burned-out pump motor
Gai-lift tlmii. Gas liftequires lest maintenance than either rod and beam orpumps It includes "downhole retrievable"valves, and mandrels, all of which can be operated from the surface by wireline tooli The relaied wire line tools (whith are lowered into the well by small-diameier steel cable) and special woikovei rigs pel mil rapid workoveit and minimum downtime (oi repairs, but these advantages are lurgely offset by the much
greater initial capital costs of gas lift the gal must tic brought to ihe oilfield and com pe cited before it can be used. (If (his initial cost is included, the US-made submersible pumps are economically as efficient as gas lift over the life of the well, despite their more frequent repairs )
0 there were onlyas-lid wells in the USSR, but this number would ai least double and might increase tenfold0 if the Soviets could acquire (or copy) and assimilate more o( Ihe beltce US gas-lift equipment and technology,his event, Ihe Soviet need for high-capacity submersible pumps could be lowered by aboulercent, withsavings in maintenance manpower. This scenario is unlikely, however: gas lift requires longer leadtimcs, associated with supplying and installing the necessary compressors, downhole equipment, and gas supply pipelines
Currently, theell Samotlor gas liftit al least two or three years behind schedule Theell Federovo project ii nestingbul il was also delayed. Both projects were supplied wiih critical US gas-lill equipmentS affiliate in Ireland. Other fields slated for gas lift operations include Bars* Gelmes. Kolur Tepc, Uzcn-Zhclibay. and several offshore fields in the Caspian Sea
Hydra-He Pumpi. Hydraulic Irodless) pumps arc installed downhole, as arc electric submersible pumps, but they are operatedutd pumped at high pressure from (he surface instead of by electric mo lots. Hydraulic pumps are being tested in (he USSR, and oil industry planners have indicaicd an interest in obtaining as many0
Werkorer Rxgi. Sttf-Propelled Units, and Oiker Equipment. Duringhe Soviet Union made no substantial progress in well-repair engineering or ihe manufacture of repair equipment The number of wells that need to be worked over each year increases steadily, however, and now cicccds Soviet repair capabilities New wotitOvcr rigs capable of
a
i
ons of pipe and of moving over sncw and mmpt terrain arc needed to service deep "clli Belter snubbing devices (small blowout preventers) are required for raising and lowering tubing in high-pressure wells. Development of new and improved equipment Is alow. For example. Soviet output of most types of cillield equipment lagged behind demand byoercent. Pump rods and workover rigs were in especially short supply, and ihe industry delivered onlyercent of the de waxing equipment needed for cleaning deep wells,ercent of the centrifugal pumps for water injection, anderccr^ of the wdlbore compressors for gas-lift wells.
Soviet oil industry managers iccogoiie lhc efficiency of Western equipment. Evidence of thislanEputting0 oil ndls on gas liflells on new hydraulic pumps. According to the Soviet technicians* calculations, the use ofequipment for these installations over the decade could yield the following savings:
od-and-bcam pumpsork over rics.
1 million well repairs.
0 maintenance workers (they planned lothe maintenance force by Ihis amount).Combined savings ofillion rubles
Tertiary Methods
The term enhanced oil recovery referspectrum of methods and techniques increasing the ultimate recovery of oilcscrvoii beyond that attainable by primary methods (natural reservoir energy) and secondary methods (artificial maintenance of reservoir energy and artificialOR extends oil production by altering the forces Ihat hold the oil in place
The major categories of EOR are thermal andThermal methods, aimed at reducing Ihe viscosity or the oil by heating, include.
Cyclic steam injection (steam soaking;)
Steam drive (steam flooding)
- In situ combustion (fireflooding)
Chemical methods (also called misCiblc flooding) arceducing the surface-tension forces between the oii and the driving fluid They include
Hydrocarbon cniseiWe flooding
Carbon dtoiide miscibtc flooding
Polytrwr-augmentedicellai-polymer flooding.
Alkaline flooding
A batic deteription of EOR methods and theirit provided In ihe appendix, and threeemployed methods are illustrated in figure 6
The lucres* of an EOR operation it criticallyon the composition and consequent behavior Of ihe injected fluidi, the accuracy of the reusrvenr engineering aod modeling, and ibe process technology employed Each reservoiriffer cm ici of technical problems, and the complex icchnolocy it not directly iranifcrable from one geologic formation to another bach Oilfield requires at least one pilot lest, lailing up to five years.ilot teat is successful, many new injection wdls have to be dulled lo bring the project up to commercial tize Aftrr these wells arc drilled and injection of heat or chemicals hat begun it may lake as long as two years foro appear at the original producing wells.EOR can be up toimes at labor intensive as conventional oil prodociioo
EOR often high potential benefits Its use can permit the uliimate recovery of as much atercent of the original oil in place (under idealhereas water flooding can be expected to lecovcroercent I'll', alsocntaiit high cost and high riskt. Latgc expenditures forquipment,and capital must be made before it can bewhether tot'!'rat ion of the process in invCCCslery expensive
1
Western oil companies' application of mam technical advances in liOR hat been slowed lempoiarily by the worldwide turplui of crude oil that hat depressed price levels. in:ieased the rnk element, ami made
c
ii. r>
9
)
activities uneconomic. Company budgets are now emphasizing projecii wiih thori payback periods, and BQR ts not only capital intensive boi alio slow to pay oft
f tbe Sewitt EOR ProgTaau
Soviet petroiearn specialisti have recognized the needncrease oil recovery from eiisting oilfieldse ears.n EOR program was not given high priorityn February of lhai yeai ihe 2Sih Congress of the Communist Party of the Soviei Union stressed the importance of providing thewith an adequate supply of fuels and energy and noted that tbe task wouldubstantial rm provemenl in the technology for exploiting oil depos-itl
In6 the deputy chairman of Gotplan. A. Lalayaots.igh-priority planlo increase oil recovery from ciisting oilfields
alled for:
timetables for adopting new recovery methods.
a special association within the Minis-iry of ihe Petroleum Industry for enhanced oil recovery lechnierues
a special fund to help cover cons incurred by oil-production enterprises adopting ihe new technology.
new plants to produce large quantities of specialired chemicals
Producing large amounts of special cquiyenrnt
Training workers.
The Commute* on Science and Tec1 -osogy of ihe Canned of Ministers wase responsible for casordi-nating the EOR program The planners hoped that by thehey would be recoveringoercent of the original oil in plao
Soviei petroleum officials have continued iothe importance of EOR endeavors. In7 the Minister of ihe Petroleumal'isev. indicatedong-term comprehensive program had been formulated for commercial use of new EORthose employingagentsolymers, and carbon
would facilitate anilequivalent to the opening of several large oilfields
In8 the Ministry of the Petroleum Industrycientificd ui trial assocsaiion for thermit oil recovery techniques, called Soyurtcrm-nefi This organization, centered ai the Krasnodar Scientific Research and Planning Institute for ihe Petroleum Industry, is responsible (or develop.or. and applying thermal Oiltraction processes, designing ihe macliinery and equipment for these processes, and supervising the operations al oilfields where these processes arc applied N. K. Itaybakov. Chairman of Gosplanormer Minister of (be Petroleumastrong belief (bat EORcouldignificant contribution to impro*-ing (he USSR's oil situation by increasing the amnum of recoverable reserves
Despite these optimistic plans and repressions of confidence, ihe program is Still in low gear.production of oil via EOR techniques is only0 barrels per dayillion tons pea year I. orerceni of total Soviet oilAccording lo knowledgeable Soviets, thermalof steam and hot water and in situfor aboutercent of (he increased yield being achieved b> use of EOR meih od
Although EOR technology will probably accounta low total yield of oil in the USSRears, the Soviets will continue to use ilfields intond beyond. ThisEOR offers ihe possibility of producingoil from earning fields, where thealready in place Therefore, dr.spue itsis claimed to be cheaper than the< of small West Sibci ir deposits and
potential new fields in East Siberia and offshore in the Arctic seas. And the Soviets can rapeci oil recovery to incieisc with improvements in technology and cti""of il io be acquired from the Wet
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EOR effort' have Men harnpernd by shortages of equpmeni and chemicals9 ihe Soviet press reported ihar domestic industri had deliveredc-cen' of the equipment foe ihal year's plannedrk ind thai much of what ii delivered was of inferior quality. Ihr inadequacies of domes lie tlcam generator! were especially noted, ashortagewo yean later ibe fml deputy minister of the petroteom industry in charge of EOR wot. Khalrmov, indicated that Soviet ma chine-build ing planti had not fulfilled ihdr plant for ihe manufac-tuie of equipment and spare parls for thermal opera-lions and that the chemical industry had not produced nearly enough chemical agents. The results of the Sonet EOR program during the pastears are su mmMiicd in table ).
Soviet Ac pi-cation of EOR
Since the. Soviet specialists havelaboratory and pilot tests on various thermal and misciblc flooding processes, with varying success. They appear to be aware of every EOR process thai has been tried in Western fields and laboratories, and ihey ate pioneers in the thermal mining of cilremely viscous deposits and the nuclear stimulation of oilf the major IsOR projects conducted or planned is shown ia table a. EOR Iceheaqiics applied or planned at major oil fie Idschcrrvical (polymer) flood at Arlan. mrsolble Hood at Rornathkino, ihcrmal methods at Baku, and thermal mining al Yarcga.
he giant Arlan fieldajor produce of heavy, viscous oil. Output has been declining steadily since peak production was reached in th?. Tie nature of Ibe reservoirs at Arlan is such that polymer flooding is the only technique lhat offers reomtse (or increased oil recovery, aad the Sennets have been experimenting with it (here6 They are still in the eaperimental stage. Potymei injection on the large scale required ai Arlan haa never been employed before: its effectiveness is uitccr-tain, aad ihe cost and risk would be very Ugh. In any case, the Soviet chemical industry cannot curienily supply polymers in the amounts neededull-scale polymer flood at Arlan.
"Sec Nh'AC Inieltigracc Aiuuini OS It-iOi'. fT 1
rmuwvli fy. Mere MtfiyArt* fGMS v
Table J
Oil Produced by Enhanced Oil Recovery Methods
TWel
J]
1
This mature supergianl oilfield has
dominated oil production in ihe Tatar ASSR since che;7 It was the largest oilfield in tbe USSR, in terms of both production and reserves.
Il still ranks second only lo the Samotlor fieldajor producer, though Its output has been declining aftereak ofillion tons in ihe early
.
The Soviets consider the carbon dioxide method of EOR the most suitable (or condiiions xi Romashkino and have announced elaborate plans for its use there. Because of tbe cociplex nature of the producing formations (already damaged by the way in which waterliocding was appbel earlier inpmshe Soviets probably cannot use CO, in more than( Ihe field'sroducing areas. Even so. however, (his project would needimes as much CO, as may be availablehemical plant built near Tot'yatliest German firm.
Even if nilficie.il CO, were available, the Soviets probably would recover no moreillion ions of additsonal oilyeae period. This wouldery modest returnery high cost The Soviet! appear to be having second thoughts about therecently delayed indefinitely tbe con-strociion o( the pipeline lhat was IO deliver the CO, to ihe Romashkino area.
S.sis- At to. Production at Baku, the oldest predicting oil region of the USSR, hat been declining despite etTorii to explore and develop new fields in the offshore areas of the Caspian Sea. Since.
t
TaNe4
ieed Oil Reeo'Cry Projects
r
rtKibodi have been applied in several oilfields in Ihe region and have provided small addilional yieldi of oil During ihe five-year, applica-lioo of surfactants to oilfields in ibc Kura flood plain facilitated Ihe output of anons ol oil. steam injection in oM deposits near Khorosany produced an0 ions of oil. and in situ combustion ai old oilfields near Ramaninskoye and at tbe Ariem Islands produced anoo
Shoncomings abound in EOR work in the area, however Open Soviet sources describe producen at reluctant to experiment as long as there is no prospect of an immediate payoff, equipment shortages persist, and much of the available equipment is of poor quatitv
Kflrega. The field at Yaregaighly viscous crude that is not recoverable by conventional means. To exploit it, the Sovietshermal mining method that has been in commercial usehey claim that it permits recovery ofeicent ol the original oil in place
In the thermal process, two mine shafts arc sunkevel above the pay zone, and horiiontal passages are drilled and blasted to form galleries for underground drilling and produclion Operations From these gallei-ies shallow productionslanicd ordrilled into the reservoir Steam isand ihe resulting flow of oil and water is
channeledump Oil il I't-ir airii from the water and pumped locentral eolWiing point, where it is bcalcd and pumped lo storage tanks on lhc lot face "*
DcpcnoVtace on Western
Ai Ibe Soviets seek lo inacaie tbc appti. it,oc of EOR technology, their reliance on Wcttcrn cquiprneal and know-how will continue until they can train their own personnel and develop Ihei' ownS the Soviet Union has entered into negotiation! and signed contract! with US. Japanese, and West European firm, (or the supply of EOR eQuipment, chemkali, and plant* to produce carbon dioxide and surfactant/
In ihe fall7 an Italian film. Presiindustnn, wasillion contract tolant for the annual productionons of luifactanis for tertiary oil recovery. It wai to haveul no report! of tti operational Slates arc yd available. Two carbon diotide itquef act tort plants (together valued at SIS million) were ordered8est Ccrrraaa eoanpany. Borstg. to support rviscible Hooding operationi One of these,apacityillion tons peit built near ToTyailirsctble flood proiect at ihe Romath-kino deposits TV second,apacity of tOO.COO tons per year, was to have been installed at Kemerovo in Siberia; information oa its status is not available.
The Tol'yetti plant will take the CO, producedyproduct at nearby ammonia tynthesit plants and liquefy it. To use lhc lusnd lor EOR projocii. the Soviets will have tom pipeline lo the Pornashkino fields, plus pumping tutarm. CO,equipment, and CO, inject ion facilities. Inhey beganing with US. fiend. C
Ifararas lexhu CO, floodbut1 they downplayed it for various reason* lo1 they claimed that rl was delayed Indefinitely because of uncertainty about CO. supplies from the ammonia planls and disagreement oner the CO, should bt piped in gaseous or liquid form In2 the project was reported to be "on the sheir" because cither projects had higher
For thermal EOR work,USSR puiLhatcd t) high-capacity it cam generatorsS firm in1 for use in pilot projects in five old oil-producing areas. None was placed in operation bcloteecause of the lack of competent Soviet persorincl. The Soviets apparently had appropriated SSI million1 foe purchase of US steam injec-tiota cquipmcni to increase oil production in the Baku regionillion tons per year and ai Ihe Uten' oilfield in Mangyshlak5 million torn per year. Aflcr the US embargo on sales of oilfield equipmenthe USSR was imposed in that year, the Soviet began trying to ob"*'- Western-buili irmicensing"agree meatb firm, butdditional units have been acquired to datr
Inoviet officials itated ihai efforts to obtain Western tteam generators and EORhad been suspended indefinitely for lack of hard currency. According to Soviet petroleum cipcrts. however, any future purchases of steam generators would have tournkey package because Soviet petroleum engineers and technicians cannot properly use ihe equipment already obtained Without Weslern equipment and technology, the Soviet EOR program probably will remain intignifican
Put as and Prospects forbc Soviet enhanced oil recovery program is unlikely to achieve significant increases in oilnd probably will never reach the goal (letf recovering an additionaloercent of the originallace. The evidence shows ambit sous plans repeatedly being downgraded as the realities of the task ilrikt horn
eputy minister of the petroleum industry revealed that tbe USSR wanted to obtainillion ton* per year of oil from EOR open Goo*ut he Emitted that ihii timetable could not be met because of serious technical and bureaucraticew months later hethai this goal wai to be9 oil industry planning document indicat ed thai oil recta-ery from EOR methods would reach
-Sen
illion loni57 million IonsAnnouneeinentsreated thaio( oil to he obtained fromould he double (he more0 Dul in October
int Deputyhalimew. tbe director of EOR efforts in the Oil Miniiiry. was dismissed lor falsifying data and waning materiacalling further doubt aboul the realism of Ihe Soviet EOR coal.'
In ha need iccm-eiy operaiioni are oftenby Sonet tpedaUiutrai(htforwaid devescpmeai and application of am tcchac4ogics But. when new technique* (developed and tested under laboratory or pilot protectrebe field to heterogeneous Oilfield reservoir atruetures and per-rncabilitiea, unfareaecn difficulties can crop upto cope with there difficulties arc verycareful management and control, large quantities of spoiialiied chemical! andand coniidceablc time On ihe baits of the revised plam and Soviei performance thus far, we judge that oil production liom EOR methods -ill reach onlyillionnd no more lhanillion tonsf
Secee-l
Appendix
Oil Recovery Techniques
Enhanced oil recovery (EOR) rot,hods are generally eaierpjrized at .hernial and mndble. Thermal meth-cdt arc ooniidered to be the most advanced, and aTargc-scale applications are under way in several countries. Field tests of the miteible noodingare under way. as well at some commercial
Thermal Methods
Thermal methods are aimed at icditeing tbe viscosity of tho oil by_ beating and. in some cases, changing the characteristics of the oil. These methods are most widely used for highly viscous, low. gravity crude oils oecurrinj at shallow depth:
Cyclic Slemm Injection (Steamigh-pressure tieam generated al the surface is injectedroducing well for several weeks. Then the well is capped and allowed tofter four toeeks, the well is placed back on production and theoil and water arc allowed to bactflood to the surface. As the pressure in the well de-rreases. some of the water that had condensed under pressure from the injected steam vapor im and drives heated oil toward the producing well. Oil pioduciion is highest when the well ii First rrnpencd and declines as tieam isWhen it hat doclittedredetermined level. Ihe entire cycle can be repeated, but the process gradually become* less efficient. Because of its cyclic nature, the process is often called tbe huff-and-puff method of oil recover;
The value of cyclic it cam injection lies not so much in improving ultimate recovery as in increasing lhc oil-production rale. The average rate when the well is reopened faoimes the pretreatment rate. The major irtefTieieney of ihe process ts the loss of beat. It is not useful in strata of oil-bearing sand' thinner thaneet, because ton much heat escapes to Ibe rocks above and below
Steam Drive (SteamflooJiiigJ. This process involves the continuous injection of Steam or hot water,ixture,roup of outlying wells to push oil toward prxduciag welb. Iteries of icmpera-tttre zones in the reservoir: nearest the Injeciion welliteam zone,one of hot water, whichone of hot water plus oil. The steam and hoi water heal the oil. rtaisoving il from the deposit and forcing it io the producing wdti.
Steam drive fa likely so be tbe technique most widely applicable. It recovers an additionaloercent of the original reservoir oil In place, depending on ml and reservoir cha ranhe success of sproject depends on the rapid, continued growthteam zone with rcsnlting high rales of oilHeat tosses must be minimised. Tbe major practical problems are Isolating the geologic rone to be steamed, injecting tieam into selected wells,the hot wells, handling the excess associated water production. conUolling the sand produced (io avoid land-plugging of the well or of lines at the mirfaeej. and coping with ihe weakening effect of highon the equipment
fn Sill. Camk^stian(nrtflt>oJX This is anotherof healing the oil in ibe reservoir to reduce its viscosity. Atr fa injected into ihe reservoir, providing oxygen so that some of the trapped oil will burn Combusiionmay be spontaneous when the injected airflow it large enough to cause gat saturation,eater may be lowered to initiaic combustion. Heal from the burning oil thins the remaining oil. partially vaporizing it. and the steam, hot water, and hot gas
' flaUine (betOCOnty rate fromerceni of oil I" planj percent actually reeoten onlycrce" of OIPhe practical lemii lor project! ft il.ii nalore
.Seerer^
li) the fire puih (hit more fluid oil toward the prod acini wells Utuallynjected through one vet of intctlockine wells, and oil is produced from another ser
The three balk types of ui illu inocesses ate:or forward combustion; wetornblnation of forward combustion and waterflood. and reverse combustian In forward corn butire il itailed In the formation at the bottom of an injection well. In wetimilar file ii started, then water is injected alternately with airransfer heat (ia the form of water vapor) from tbe burned reason through aad ahead of the eornbustion front In reverse combustion, the reserve* eel is ignited at the production wells rather than at tbe injection well.'
in situ cornbtisiuKi it the most difficult of the tertiary processes to model and predict. Most of the operating problems arise from the high temperatures involved. Thermal stresses on cement, pumping equipment, and tubing increase the frequency ol Iheir (allure, and the composition of the combuition gales, together with highccelerates cori en ion problems. Sand production causes clogging and severe wear (abrasion) in pumping rqulpsnen
MiseiWr Methods
Misctble methods of enhancing oil production arc aimed al reducing tbe surface-tension forces that bind ihe oel to roe* These include Ibe use of hydrocarbons and Carbon dsdaads and tbe chemically augmented methodsellar, and alkaline flood,m
ttti flawdiag. lighl to intermedi-
ate-weight hydrocarbons -such as dry gas. propane, butane, and liquefied petroleum fasto mil with Ihe reservoir cal.ank of oil and driving it toward producing wells Thisrequires high jx enures and is limited to (airly deep fields, where the threat of rupturing the cap rock is small It is also energy intensive, not only because tbe mttclble slugydrocaibon derivative (that is. il uses oil to.1'oil) but also because compression is (cquiera
Carton Dioxidi Mitritlr Flooding. tn.ectedin crude oil, reducesand in-
creases its permeability and bulk. The swellingreservoir pressure, while ihe (educed viscosity lets the oil (Vow more readily toward Ihe productionlug of water injected after Ibe slug of CO, drives the gas away Irom the injection well. When CO, appeart at the producing welt, il it recovered, cleaned of impurities, compressed, and reinjected
Carbon diotldc flooding appears to be ihe nvoat promising of ihe misctble methods However, its use probably will be limited io fieldt of light oils that are relatively close to soutoes of CO, because theand transport of the gas ispensive and energy intensive The effectiveness of this EORdepends greatly en reservoir bcunogeneiiy. and ai best il can probably recover no more lhano IS percent of Ihe Oil remaining aflee waterIV*V
folymir-Angmnild (fCnkaactd) Walu'loodint. Chemical) with high risriccular -fichu (polymers) can be added to irdocied water io inciease its effective viseosily and ill efficiencyrom to drive oil toward producing wells. The increased 'iicosilythe ftow of water in tbe reservoir formation and icsprovea Ma ability to sweep oui Ibe oa! The use of polymers reduces the ralio of wai" io oal and thus reduces overall operating cost-
Enhanced waieiflood can poteniially recover more of the original ml in place lhanlain wnierfTood Howevei, the rale of oil recovery with eilhei method ii Ihe same during ihe first (ew years of operation. Moreover, enhanced waierlsooding poses formidable engineering problems, and there arc no well drr"ed measuring, techniques lo Optimne the procea-
MuttUi Polymvr floodingWmgl
This category of EORumber of processes based on the infoction of detergent solutions.are employed io wash ihe rcsctvoii foeV. much as laundry dclcrgeni washes away greasy stains. In a
micellar flood.water slugmail amount of surfactant it infected into the reservoir. The aoiulkxi is calledccauie iu conccnira-lion iuses the suifactani moleculealing together in dusters called micelles. Because the mierocrnulsion formed is mtscabte watfa oil, it dissolves the oil in ihe formation. At the same time. Ihe emulsion reduces inteefaciai tension between ihe oil and water, permit-bng ibe eel to flow freely out of Ihe rock ports "
As is tbe case with meat EOR processes, eachflood must be precisely designed for the specific reservoir. Tbe conocntiaiiona and types ol chemicalt used will depend on tbe crude oil composition, ibe reservoir temperature and clay content, and the ion ConccnUatrOns in the rcaervoii water. The surfactant injection must be carefully designed for minimum absorption by the potous media in the reservoir andit mum sweep efl
Caustic chemicals like sodium fcjtfrtMsck or sodium silicate (educeafic si tension between the infected fluids and (he reservoir oil. Added to injection water, they form surfactants within the reservoir by neuirahnng ibe petroleum acids. Alkaline flooding processes are stillesting stage. Then success dependt on the chemical and physical properties of the reservoir materials, ihe composition of ihe crude oil, and the effectiveness of surfactants formed when the caustic chemicals react wiih different acidic compounds in Ihe reacrraii
l
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