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SPE30303The Feasible Conditions Study of Steamflooding for Heavy OilReservoirs In China After Cyclic Steam InjectionZ. He, R. Zhangq , H. Y. Pu, X. Ran, RIPED of CNPC* SPE Member

~~t 1555, Sociify of PafrofaumEn@nmrs,inc.ms paparwasprapard fc+prasanfafionatffm InwrrafionafHaavyOifSympdtnn haklinCnfww, Afbrla, Cabl 1S-21 J-l*.

ABSTRACT

Ch ina is r ich in hea vy oil reserves. In r ecent t enyears, the product ion of heavy oil has rapidlygr own t hr ou gh a pplica tion of st eam in ject ion a ndt he a nn ua l pr odu ct ion r ea ch ed u p t o 11.9 m illion

heavy oil reservoir s, systemat ic studies havebeen condu ct ed t o invest iga te t he effect s of oilviscosit y, oil forma tion t hickn ess * ver tica l per -meabilit y d iffe rence , r ep roduct ion r a t io of in ject -ed water in steam cycling and channeling pa thetc. on steamflooding effect iveness. Then ~ a

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2 FEASIBLE CONDITIONS STUDY OF STEAMFLOOD FOR HEAVY OIL RESERVOIRS IN CH INA SPE30303

method of heavy oil product ion . Meanwhile,stea mflooding pilot test an d developm e~t testhave been under way at var ious typies of heavyoil r eser voir s. Fou r h eavy oil pr oduct ion basesh ave been set u p in Lia oh e, Sh en gli ,Xin jia ng a ndHen an oiifieids. In i 993, mor e t ha n 9,000 cyciicst eam in ject ion oper at ion s h a d been conduct ed inabout 6,000 wells and more than 200 pa t ternsA-.,- ha-n in prece~~ nf st esm f lnnr l ing, ~~~ ~~..a-vb k%.. . . . . -. - . . . ..V . . . . .nual heavy oil product ion in 1993 and 1994reached 11. 9 million and 12. 3 million tons re-spect ively, which a ccou nted n ear ly 1/10 in t hena t iona l t ot a l oil p roduct ion .At pr esen t, cyclic st eam in ject ion becomes poorwit h in cr ea se of st eam in ject ion cycles (F ig. 1).Th e effect ive per iod sh or ted, OSR declin ed a ndeconomic benefit decreased. According to thest at ist ica l da ta , t he cyclic st eamin g wells a bove 5cycles h ave a ccou nt ed 36.1 % of t he t ot al cyclin gwells ~ and OSR has been O. 49. Cyclic steam in -ject ion h as en ter ed in to t he m iddle a nd la te st ageand fa ced th e ch allen ge of con ver tin g t o steam-floodin g. In som e r eser voir s, t he complex pr ob-lem of low re-pr odu ct ion ra te of in ject ed steam(or wa ter ) appeared (for example, less than

steam in ject ion , OSR has also been lower , re-su lt ing poor economic benefit . By Sept . 1994 ~product ion Weiis of steam floodin g in th e whoiecount ry numbered 789, with average daily oilpr odu ct ion per well on ly 2.0 t /d a nd a nn ua l a ver -a ge GSR 0. i66.Beca use t he m ain dr ivin g for ce in t he pr ocess ofcyclic st eaming is na tura l pressure energy in~e~erVQir~ a nd it will be exh au st ed! it is difficu ltfor cyclic steam in g to obta in h igh oil r ecover ya nd good u lt im at e developmen t effect iven ess.E nh an cem en t of oil r ecover y m ust r ely on effic-t ive dr ivin g pr ocess. Th er efor e, cyclic st eam in -ject ion must be effect ively con ver ted t o st eam-floodin g in or der t o gr ea tly en han ce t he over aHheavy oil development .E ffect ive conver sion con sis ts of two a spect s. Th efir st is, for heavy oil reservoirs suitable tos teamfloodin g ~ fa vor able con dit ion s s hou ld becr ea t ed a nd cyclic s teaming shou ld be t imely con -ver ted t o st eamfloodin g t o en ha nce h ea vy oil r e-cover y; t he secon d ~ for h ea vy oil r eser voir s n otsu itable or tempora r ily not suitable to steam-flooding, pot en t ia l s hou ld be a na lys ed a nd effec-t ive measu res sh ou ld be developed and taken to

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SPE30303 Z. HE, R. ZHANG , H. Y. PU , X. REN 3

pr oblems and r es er voir con dit ion s va r ia t ion s oc-cu r ed a ft er lon g t ime cyclic st eam in ject ion ~ s u cha s low r epr od uct ion r a te of- in ject ed st eam ~la r ged iffe rence s of ver t ica l a ct iva t ed ext en t of oil for -mat ion and ser ious steam channeling in cyclicst eaming et c. It has been recongin ia ed t hr oughs team floodin g pilot s t ha t t h es e fa ct or s can gr ea t -ly in flu en ce st eam flood in g. S imply s cr een in g t h er eser voir geologica l con dit ion s will n ot lea d t opract ical cr i ter ion of s teamflooding.Therefore, in th is paper, a comprehensive re-search approach has been adopted ~ tha t is ~ ac-cor din g t o t h e geologica l con dit ion s an d pr od uc-t ion condit ion s in cyclic s t eaming and r efe rencingt he st at us of st eamfloodin g pilot s ~ bot h a spect sof geologica l a n d pr odu ct ion con dk ion s a r e s tu d-ied on the basis of three typica l types of reser -voir s (block, m ult i-la yer a nd sin gle sa nd body)u sin g t herma l r ecover y n um er ica l sim ula tion t ocompr ehen sively det erm ine th e s cr een ing cr it e ri-on of st eamfloodin g fit ta ble t o t he pr esen t t her -ma l r ecove ry t echn ica l s it u a tion .Th e st u died geologica l con dit ion s in clu de oil vis -cos ity, fc:mat ien th ickness, ve .r t ica !permeab ilityh et er ogen eit y of format ion , a n d pr od uct ion con -d it ion s in clude ve rt ica l a ct iva t ed ext en t of forma-

RESERVOIR GEOLOGICAL CONDITIONSSUITABLE TO STEAMFLOODINGEffects of Oil Viscosity and Oil FormationThickness.In the process of steamflooding for heavy oilt h ermal r ecover y, oil vis cos it y and oil format iont h ick nes s a r e t h e ver y impor t an t fa ct or s in flu en c-in g st eamfloodin g per formance. F or example ~ ifthe oil viscosity is too h igh , up to 104 or 10s cp,a nd t he oil forma tion is t oo t hin , st eamfloodin gthese heavy oil reservoir s will hardly achievegood t ech nica l a nd econ om ic r esu lt s. Th e effect sof oil vis cos it y and format ion t h ick nes s h ave beenst udied a t t he t hr ee t ypica l t ypes of r eser voir s a smen tion ed befor e. F or block r eser voir , t he st ud-ied form at ion t hickness include 15m, 25m t 45mand 60m; for mu lt i-la yer r eservoir ~ 10m ~ 15m ~20 m and 30 m and for single sand body reser -voir ~ 5m * 10m ~ 20m. At differen t format iont h ick ness , va r iou s oil vis cos it ies h ave been s tu d-ied. They are 500cP, 2. OOOCP, 5, 000cP,10, 000cp and 20, OOOcp at r eservoir temper-ature .Res ea r ch r es ult s (F ig.h igh er t h e oil viscos it y

3-6 ) indica te tha t theand the smaller the for -

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4 FEAS IBLE CONDITIONS STUDY OF

poor oil recovery (Fig. 4 ) because ofSTEAMFLOOD FOR HEAVY OIL RE SERVOIRS IN CH INA

stronggr avit y sepa ra tion of in ject ed st eam, t her efor e ~t oo la rge t hickness will not be appropr ia t~ a ndm iddle t hick forma tion (

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SPE30303 Z. HE, R. ZHANG, H. Y. PU, X. REN 5

Effects of ChannelIing Path Formed In CyclicSteamingAt Ka rama yi oilfield in Xin jia ng, Sh ajia sh i oil-field in Sh en gli a nd some a rea s in Lia oh e, ser iou ssteam channeling occured genera lly in cyclicsteam inject ion . In the process of enla rgedst eamfloodin g a t Ka ramayi N o. 9 dist rict ~ st eamcha nn elin g is also pr om inen t. In t hat wa y ~ howdoes cha nn eling pat h a ffect st eamflooding if ith as been formed in t he r eser voir t hr ou gh sever als teaming cycles?Single sand body model has been used to studyth is matter . -- - -A I.A.a ..1m c~ness of ~a llU UUUY k 1 !k n ~wit h 2m sh ales in ter sper sed in sa nd body. Ch an -n elin g pa th is r epr esen ted by a r egion al ver y t hinla yer in t he m iddlle of oil forma tion .As shown in ta ble 6, t he resu lt s indica te t ha t t heoil r ecovery and OSR of steamflooding are de-crea sed 51% and 39% r espect ively by t he ch an-neling pat h exist ing in r eser voir . Cha nn elingpat h form ed in cyclic st eam ing grea tly a ffect ss t eamflood ing per formance? d isplaying as low oilpr oduct ion of 1 z 2 mont hs, shor tly incr ea sing,

Ch in a in t he pr ocess of cyclic st eam in ject ion , forexample, Gaosheng oilfield and Du-66 blockdemon st ra te RPRIS on ly 15% (RPRIS m ea ns t hera tio of qua ntity of produced wa ter t o t hat of in -ject ed cold wa t er -equ iva len t st eam ). Th e r ea son sof th is problem are complex, many aspect andnot t ot ally known. By fa r, a ccordin g t o t he a nal-ysis, the possible reasons may include the fol-lowin g a spect s: mor e wa t er -wet t abilit y of r ock a th igh tempera ture condit ion; oil emulsion andblockin g; swellin g of cla y m in er als, especia llyt he n ew m in er als gen er at ed a t h igh t em per at ur e(m ain ly sm ect it e ); pr oduct ion pr oblems. LowRPRIS in dica t es poor flowin g abilit y of t h e liqu idin reservoir , !m!ing to both oil and water pro-du ct ion bein g low level. Deepen in g discu ss ion ofthe reasons does not belong to the scope of th ispa per . Wh at t his pa per is in vest iga tin g is just it seffects on steamflooding .The block reservoir and mult i-layer reservoirmodels ha ve been used for t his st udy a nd t he pa-r amet er s of oil vis cos it y an d format ion t h ick nes sa re also as th e same as before.The studied result s indica te tha t as RPRIS de-

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6 FEASIBLE CONDITIONS STUDY OF STEAMFLOOD FOR HEAVY OIL RESERVOIRS IN CH INA SPE30303

re se rvoir s su it able to s t eamflooding.CONCLUSIONSBa sed on t he a bove st udies a nd r efer en cin g pr e-sen t st eamfloodin g scr een in g st an da rd (t able 7,ref. 3 ) * th is papar proposes a comprehensives teamflood ing scr eening cr it er ion , which ha s t ak-en t h e p res en t pr oduct ion t echn iqu e a nd develop -ment condit ion s as evalu at ion bases (table 8).For the reservoir s feasible t o steamfloodin g atpr esen t * t he main poin ts ca n be su ninmr ized a s:1.

2.

Oil viscosity and oil for mat ion th ickness areim por ta nt fa ct or s for st eamfloodin g. OiI vis-cosit y sh ou ld be less t ha n 10, 000cp; Gen er al-ly, oil for mat ion t hickn ess sh ould be grea tert han 10m ~ specificly for mu lt i-la yer r eservoir sgreater than 15, meanwhile, it is a lso nots uit able for format ion t hicknes s t o be t oo t h ickand middle thickness less th an 45m would befavorable.Ver t ica l p ermeabilit y h et er ogen eit y of oil for -ma t ion may grea t ly in fluence s teamflood ing ef-fect iveness. The st ronger it is , the la rger lyt he oil r ecover y decr ea ses. Th e fa vor able ver -

Low re-pr odu ct ion ra te of in jected steam r e-sults in abun dan ce of water exist ing n ear th ewell and in tu rn lower s heat in g efficien cy inthe dr iving process ~ and the performancewou ld be poor a ft er conver t in g t o s teamflood-in g. The fit t able r e-p roduct ion r a te of in ject edst eam in cyclic st eamin g sh ou ld be n o less t ha n35-40%.

6. The above conclusion s are just based on pre-sen t pr odu ct ion t ech niqu e a nd developm en t..--..l:+::a... .GA qL*.* -a --1- ;.r a A mAw.nmci_U(J J1U1 L1lUILD 9 CULU LAKY & G A GLm t s W. J AS w .-.sbQmen t of pr odu ct ion t ech niqu e a nd a dju stmen tof developmen t syst em , t he scope of h ea vy oilr eservoir s fea sible t o s teamflood ing will be en -la rged. a nd t his scr een in g cr it er ion ca n be fu r -t her r evised for mor e per fect ion . In a ddit ion ,they are also genera l ~ for pa r t icular reser -voir s , some mod ifica t ion s migh t be neces sa ry.

ACKNOWLEDGMENTSom e r ela ted t ech nica l wor ks fr om Qin sa n Yu eand P eigong Sh ie, s en ior engin eer s in t h ermal r e-covery dept . of RIPED is gra tefu lly acknowl-.edged. The auth ors a lso wish to thank t he helpsof ot h er collea gu es in RIPED.

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SPE30303 Z. HE, R. ZHANG , H. Y. PU , X. REN 7

cy , Presented at the fir st China-CanadaHeavy Oil Technology Symposium, *qhuoZhou , Oct . 26~30, 1987.

5. Xia , Y. E. and Yang, H. X. etc. : Charac-t er ist ics and Recover y Met hods of Heavy OilReser voir s in Liaohe Oilfield, Pr esented att he fir st Ch in a-Canada Heavy Oil TechnologySymposium, Zhuo Zhou, Oct . 26z30, 1987.

6. He, Z. and Zhang, R. etc: EnhancingSt eam floodin g E ffect iven es s St u dy for Th r eeTypes of Hea vy Oil Reser voirs, RIPED Re-por t, Sept . 1991.

Table 1Oorldit iom I!-

011Vlsooslty,p.011Formalion Thiokness, mGeologlcsl V@i@l Permeet)!l!iy He@fQ-

sent at China Heavy Oil Thermal RecoverySymposium, May, 1993.R. T.i st n . C ~., : .St eam f lnnAinu P~r fnrm snm= ~~ . ---- , - . --------------- ~ . . . . . . . . . . . . . .No 9 Dist rict Ar ea in Ka rama yi Oilfield, P re-sent at China Heavy Oil Thermal RecoverySymposium, May, 1993.

9. Zhang, L. P. : I nflu en ce Analysis of Ver t i-ca l Act iva ted Ext en t of Oil F orma tion in St eamInject ion, Pr esent at China H ea vy Oil Ther -m al Recover y Symposium, May, 1993.

10. Zhang ,L. P. and Bao, L. C. etc. : Steam-fl .--l: 13-_t ------- xmucnng rer lurmanm in Shu 1-7-5 Pilot tD-..am+ a+ Pk :ma U,m..,., ~~! l%am .-.m l Re.-~..L A cacmc ab w naua A Aca vy A LLGL A8AaA ANGUJV -nrw Cwmnn.i * *m . M.v. 1 QQ2b. , , .* * p * u ..* , ..* -J , * .

The Studied Items and ContentaTyBaofReservoirs OQ@ents

Block Multl+eyer Single Send Badyd d d 500,2000,5000,200004 4 4 5,10,15,20,25,45,60g ~ ~ vpv~EQ, Q Is r). 3 0. ~~,~. ~~,-: -.-: --

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8 FEASIBLE CONDITIONS STUDY OF STEAMFLOOD FOR HEAVY OIL RESERVOIRS IN CH INA SPE30303

ProductionarametersTable 3 ProductIon Pmsmeters of Steam Injection

Types of ReservoirsBlock Multl-Lsyer Single Sand Body

At cyclic Steam 4ectionInJecUng Intensity, ( t /m)4ecting Rste, (t/d)Wellbore Pressure, (MPa)Wellbore Temperature, (C)Wellbore Steam Quslity, (%)

At SteamfloodIngIaJectlag Rate, (t/d)IaJectlng Pres&re qt Wetlbore, MPaWellbore Stesm Qa81ity, (%)

80 80 80200 200 50-10016.0 16.0 6.0340 340 27040.0 40.0 60.0

160 140 6016.0 16.0 6.040.0 40.0 70.0

Table 4 Vertiul Permeability Dtstributton for Block Tyw of Heavy Oil ReservoirVerticst Permesbillty Dlstrlbutlon, mdVPVC= o VPVC=O. 3 VPVC= 0.45 VPVC=O. 65 VPVC= 0.85(DK=l.0) (DK=2. 8) (DK=4. 47) (D, =14. 5) (DK~122)

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SPE30303 Z. HE, R. ZHANG, H. Y. PU , X. REN

Table 5 Effects of Vertlcd Activated Extent of (Xi i b~~i i~i i ~i i ~:ex =f!d i~Types of Reservoim VAEOF, % Time, d Dxily Oil Production of Single Well, t/d OSR

Block

Multl-Layer

Single Sxnd Body

10050332s10050332s100503325

276029603124326012431078765760157917261765~?g~

12.511.610.910.69.27.87.36.65.04.23.93.8

0.2340.2170,2040, 1980.1980.1670.1560.140.2520.2100.1960.188

9

Oil Recovery, %

17.617.517.317.321.515.710.49.420.118.9180017.5

Table 6 Effects of Clmnaelling Path Formed In Cyclic Stexming on StexmfloodingIndexes Cbannelling Path No Cbxnnelling PathDriving time, Day 1200 980Dally Oil Production of Single Well, t/d 3.9 2.4ON-wan! Ratio O.196 0.120

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10 FEASIBLE CONDITIONS STUDY OF STEAMFLOOD FOR HEAVY OIL RESERVOIRS IN CH INA SPE30305Table 7 Steam Flooding Sieving Criterion and Heavy 011 Reserve Ciasslficallon Criterion

Second classon technologyImprovementin recent period

0.20>0.50>0.10>7.0

>250

Third classwaitingortechnologydevelopment

Fourth CISSSnot suitable forsteam-injectionrecoveryFirst ChSSon availabletechnologyParameter group

>50 10000 5. 1)>0.5

4.@sol@xSolRasarve factor IOMT/kmk* q m

>0.20>0.50>0.10>10.0

>0.20>0.40>0.08>7.0

>0.20>0.40>0.08>7.0

5. Permulbility (red) >250 >200 2200

Table 8 Feasible Steamflooding Screening Criterion Based on Present Thermal Recovery Technical Situation

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1-L ~ Average Oil-L_ Production Percycle of One Well~ Oil-Steam Ratio86 87 88 89 ~ ~ 92 93

Time, Year

Figure f OSR and Oil-Production Declining Curve from 1986 to 1993

, ~. ... . . . . . . . . . . . . . . . . . . . . .

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0.40.350.3

9< 0.25?! 02

0.150.1

0.050 5000 1O(D(MI 15000 20000 25000

O il V is co si ty . cpFigure 3 Steamflooding OSR vs. C)iiViscosity and Oil FormationThickness for Biock Type Heavy Oii Reservoir

o 5000 llmO 15(HIO 2(KKm 25000Oil Viscosity. cp

Figure 4 Steamflooding Oii Recovery vs. Oii Viscosity and OilFormation Thickness for Biock Type Heavy Oii Reservoir

0.240.220.2

~ 0.18~ 0.16

0.140.120.1

\ ~ l+=lOm

o 5000 lL1100 154mm z~ -Oil Viscosity. Cp

Figure 5 Steamflooding OSR vs. Oii Viscosity and Oii FormationThickness for Muiti-Layer Type Heavy Oii Reservoir

0.23

0.21$0 0.15

0.1

0.05

\

o 5000 lam 15000 20000 25000O il V is co si ty . cp

Figure 6 Steamflooding OSR vs. OIi Viscosity and Oii FormationThickness for Singie-Sand-Body Type Heavy 011Reservoir

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Perme ab il it y Cmu la ti ve Fr eq u en t, (% )

Figure 7 Permeability Lognormal Cumulative Frequency Plot

(). 5000.4500,4000. m0,3000.2500 . 2 (M0.1500.1000.0500.000

Wc=o86ml

1 ~

r~.1 ~

~ B l oc k TYIX B0.9

\

~ Mult i-1aw0.8 Tyw

s$ 0.7 ~ Shrgle4and-+ BOdYTYVBa- 0.6*$0.5

0.4 \0.30., l~~~

o 0.2 0.4 0.6 0.8 1Permeabifib Variation Coefficient

Figure 9 Effects of Vertical Permeability VarationCoefficient on Steamflooting 011Recovery

2.5 ~ Block TYIM~ Mult l. lbpr

0.5o 0.2 0.4 0.6 0.8 1

Permeabifi& Variat ion CoefficientFigure10 Effects of Vertical Permeability Varation

Coefficient on Steamflt>oding 011 Recovery

Figure 8 Steam Saturation Field at Different PVC in Steamfloodingfor Block Multi -Layer Heay Oil Resewoir (T=1400Days)

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0 .0 -mO am - 1- mm moo alm aulo 270 0 20 0aT ime, DaY

NOChamme~hg

0.0 200 600 9m 1- EMm 1200 2m0 2400 2700 30alTlmle. Days

Existing CIhannelling

Figure 1,1 Oil Producticm CUNe for Influence of Channeling

Liqu id Product ion Curve2aJ.00 . . :0 0. ms

- 1 20 .0 0 1 60 . m O

i!fi 1 20 00 . 20 . c2u J$s ao. m 00.000i- 40.003 40.000.-:0 o.mo

0 .0 2 00 6 00 900 x600 Ima mm :urn 2400 27m mm~lme. Days

No Uhannelling

____l13l qu id Reduct io n Cunve

0. 0 200 @JIJ 900 1200 1S00 1200 2.100 a400 2700 30CIIITim e. D aysExisting Channeling

Figure 12 Liquid Production Cuwe for [Influence of Channeling

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o 0

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Sn Injec tor

Sw0.600,570.540510.480.450.420.39h.360.330.30

Figure 15

P ItPa

I1500013750125001125010000875075006250500037502500

Injutor Producer

mJ RPRIS=31% 4m hmlPRIS=SS%

bml

RPRIS=IS%

3,5503.4950,440083850,33002?50,2200,165(1,1100.0550,000

1 RPRIS=72% +mI RPRIS=31% 1}mbdIPRIS=18%Water Saturation Distribution at End of Cyclic Steamingat Different Re-Production Rate of Injected Steam- Fiaure 17 Staam Saturation Field at Different Re-Production Rate- u--- -- of [n jected Steam in Steamflooding ( T=l 120 Days )

Injutor Producer

i RPRIS=7Z% 4mRPRls-31% 4mUmls=ss%

bmPRW=lS%Figure 16 Pressure Field at End of Cyclic Steaming at

Different Re-l%oduction Rate of Injected Steam