CARBONATED WATER INJECTION FOR EOR IN ONE DIMENSIONAL FLOW WITH CONSTANT PRESSURE BOUNDARIES

Transcription

1 SCA /6 CARBONATED WATER INJECTION FOR EOR IN ONE DIMENSIONAL FLOW WITH CONSTANT PRESSURE BOUNDARIES H. Yang, L.A. Jaes, T.E. Jhansen Merial University f Nefundland, St. Jhn s, NL, Canada This paper as prepared fr presentatin at the Internatinal Sypsiu f the Sciety f Cre Analysts held in Napa Valley, Califrnia,, USA, Septeber, 013 ABSTRACT A three cpnent cpsitinal nuerical del has been develped t study the perfrance f carbnated ater injectin at cnstant pressure bundaries. This calculatin ethd includes the effects f il viscsity reductin, il vlue change and interfacial tensin variatin. T cases have been studied: High and l interfacial tensin cnditins using carbnated ater injectin. The results are cpared ith siple ater injectin. Additinal il recvery is attributed t the decrease f il viscsity and il-ater interfacial tensin. INTRODUCTION Enhanced il recvery ethds include carbn dixide (CO ) flding here the CO is iscible r iiscible ith the il at reservir cnditins. Hever, pr seep efficiency has been reprted [1] due t high bility f gas and gravity driven gas verride leading t preature CO breathrugh. Carbnated ater injectin (CWI) ay help alleviate the l seep efficiency during CO injectin, here CO is disslved in ater prir t injectin and the CO partitins t the il phase upn ater-il cntact. CWI has t ain advantages; 1) the CO disslved in the il phase changes the il viscsity and hence the bility rati, and ) experientally the interfacial tensin (IFT) beteen the ater and il phases is reduced [] resulting in an iprved verall perfrance f CWI cpared t ater injectin [3]. Early n, carbn dixide slvent flding prcess as investigated in a labratry flding experient here additinal il as recvered by the carbn dixide slutin drive [4]. A calculatin ethd has been develped fr CWI [5]. The slutin using this ethd revealed the crucial effect f viscsity reductin and il selling using CWI. Results fr high pressure icrdel experients indicate better il recvery cpared t siple ater flding [6]. Even under the iiscible CO -assisted ater flding, the results shed a significant iprveent f il recvery ver siple ater flding [6]. In this paper, a ne-diensinal three cpnent set f equatins is develped t study the reservir behavir and perfrance f CWI. A free CO gas phase is nt present. The effect f viscsity and interfacial tensin as a functin f changing pressure and CO cncentratin is cnsidered, as bth are iprtant factrs in enhanced il recvery (EOR).

2 SCA /6 MATHEMATICAL MODEL The atheatical del as cnstructed using the flling assuptins: 1) Fl is ne diensinal and hrizntal; ) There is n surce r sin ter beteen the injectr and prducer; 3) The reservir pressure is sufficiently high that n free CO r hydrcarbn gases exist in the reservir; 4) Initially CO is disslved in the il phase and bth phases fl siultaneusly; 5) CO partitins beteen the ater and il phases but there is n ass transfer f ater and il cpnents; 6) CO diffusin ithin the phases is ignred; 7) Equilibriu beteen il and ater saturated ith CO is reached instantaneusly; 8) The reservir fratin has cnstant prsity and pereability; and 9) The injectin and prductin pressures are ept cnstant. The cpsitinal del is based n the ass cnservatin fr each cpnent ater, CO and il. The syste f equatins representing three cpnents, t phase * siultaneus fl (here is the prsity, S is the saturatin, is the density rati beteen stc tan cnditin and reservir cnditin, c is the ass cncentratin, is the density, u is the Darcy velcity, K and r are the pereability and relative pereability respectively, ith subscripts and superscripts CO, = ater and = il) can be ritten as: u [ S (1 )] [ (1 )] * cc c * c (1) t x here u [ S (1 c )] [ (1 c )] t * c * c x u u [ S c S c ] [ c c ] t ST ST ST ST * c * c * c * c x u p,,,. ST r * K RC x The su f the t phase saturatins ust equal ne and the cncentratin f the CO in the il ( c ) is a functin f the cncentratin f CO in the ater phase and the partitin c cefficient ( ). S c () (3) S 1 (4) c. (5) c c The five equatins and five unnns: S, S,, p are slved using a blccentred IMPES ethd by finite differences. c, c c c CO transfers fr the carbnated ater t il thereby changing the il prperties during the flding. We assue that the CO in ater and il are at equilibriu based n the

3 SCA /6 pressure dependent slubility in il and ater. The flling relatinship describes the partitining f the CO if ater and il ere in equilibriu ith a CO gas phase: here y c, x c, respectively, and c c x x y (6) c c c c c x are the ass fractin f CO in the gas, ater and il phases, are the le equilibriu cefficients in ater-co, il-co c systes. In this study, t-phase fl (ater and il) is assued. We used the crrelatins given by Eera and Saa [7] and Duan and Sun [8] t predict the CO slubility in crude il and ater. The relatinship f CO ass cncentratins in liquid phase is given as: c c (7) c c c c The partitin cefficient ( ) f CO in three-cpnent t-phase fluid syste is defined as the rati beteen ass equilibriu cefficients c c and can be calculated fr CO slubility dels f ater-co and il-co systes. The partitin cefficient is a functin f ttal pressure in istheral carbnated ater flding. Oil viscsity decreases ith increasing CO, thus enhancing the il bility. In the istheral reservir cnditin, il viscsity varies ainly due t the change f CO ass cncentratin and ttal pressure. We used the crrelatin presented by Eera and Saa fr viscsity as a functin f CO cncentratin [7]. The ater viscsity is inially affected by the disslved CO. Lieise, the ater viscsity is a functin f teperature, pressure and salt cncentratin but nt CO cncentratin [10]. We assue that the carbnated ater viscsity reains cnstant. The il density increases ith increased CO slubility hich results fr higher pressures [9]. A density crrelatin [7] has been develped hich is calculated fr pressure, teperature, il specific gravity and the il density at bubble pint pressure. The effect f disslved CO n ater density is assued t be negligible. The pressure dependent ater density as generated fr a PVT sftare pacage. The ater-il interfacial tensin decreases due t the utual slubility f CO. Hever, due t liited literature available n the effect f interfacial tensin in a three-cpnent liquid-liquid syste, e assue a siple linear crrelatin based n reservir teperature and CO ass cncentratin. It shs an inverse relatinship beteen interfacial tensin and teperature: 0.05 c ( T 80). (8) c Fr siplificatin, the flling crrelatin is assued beteen IFT and residual il saturatin at a l interfacial tensin regin ( N/ < < 0.00 N/) [11]:

4 SCA /6 S r ( N / ) Sr. (9) RESULTS & DISCUSSION T cases are presented based n t different reservir teperature cnditins. The ai f this study is t evaluate the effects f CWI under bth l (case 1) and high (case ) IFT cnditins. The cases ere develped under cnstant pressure bundary cnditins and cpared t WI. The paraeters used in the case study are list in Table. 1. The relative pereabilities used reflect a ater et syste. The saturatin prfiles f CWI in case 1 (l teperature, high IFT), case (high teperature, l IFT), and WI at breathrugh tie (38 days) are shn by Fig. 1. Because the aunt f residual il ill nt be affected in the high IFT (> 0.00 N/), the axiu ater saturatin (1-S r ) in case 1 is the sae as the ne in WI. In the high teperature syste, IFT decreases ith increasing CO cncentratin; hence, re il has been recvered under ler IFT cnditins. This can be verified by ater saturatin prfile f case here the ater saturatin in case is uch higher clse t the injectin pint. Hever, after a sharp reductin the curve flls the sae saturatin prfile as it des in case 1 due t a ler CO slubility. The verlapping ater saturatin prfile f the three prcesses in Fig. 1 iplies the sae fluid behavir. This cnfirs the calculatin results fr previus r [5] hich stated that due t the cntact ith il the initial carbnated ater injected lses its CO and then prceeds as plain ater. Thus, the CO ves behind the pure ater in CWI. Althugh the residual il saturatin stays cnstant ith bth CWI and WI under the high IFT, an additinal il recvery is bserved ith CWI. Fig. shs a cparisn beteen ater saturatin prfiles f case 1 and plain ater injectin after 00 days at injectin. The reservir rc is saturated ith re ater using CWI cpared t WI, as tie prgresses. This is ainly because f the il viscsity reductin ith increasing CO cncentratin hich can be seen fr Fig. 3. The teperature in case is uch higher than the ne in case 1 decreasing the interfacial tensin accrding t eqtn. 8. Fig. 4 shs the change f residual il ith CO slubility in the il phase. Once the CO ass cncentratin reaches 56%, l IFT is established leading t ler residual il saturatin. The cuulative aunt f il prduced in case 1, case and ater flding are pltted in Fig. 5. The CWI, ith a l IFT, has the best result flled by CWI in a high IFT cnditin. Cpared t CWI, less il can be recvered by ater flding. CONCLUSION In this paper a cpsitinal del as develped t study the perfrance f carbnated ater injectin ith cnstant pressure bundaries. A cparisn as ade beteen carbnated ater flding and plain ater flding. The results sh that

5 SCA /6 additinal il recvery using carbnated ater injectin is due t the il viscsity reductin by disslved CO. In additin, if the IFT can be reduced dn t a certain regin, significant increase in il recvery ill be bserved due t reductin in residual il saturatin. Hever, since this certain regin f IFT can hardly be achieved by regular CWI, the il viscsity reductin plays the ain rle in il recvery enhanceent. Figure 1. Water saturatin after 38 days Figure. Water saturatin after 00 days Figure 3. CO ass cncentratin & il viscsity after 00 days fr case 1 Figure 4. CO ass cncentratin & residual il saturatin after 00 days fr case Figure 5. Oil prductin after 00 days

6 SCA /6 Table 1. Paraeters used in case study Data CWI CWI WI Data Case 1 Case Case 1 Case T ( C) ST (g/ 3 ) 874. in c _ ST (g/ 3 ) 999 c c _ in c c _ res c c _ r res c r 1S Sr 0.8( ) 1S S c r S r S c 0.5 L () 100 r r WI S Sr 0.( ) 1S S p in (MPa) ϕ 0.18 p res (MPa) 3.1 K ( ) p ut (MPa) 3.0 μ i (Pa.s) μ (Pa.s) REFERENCES 1. Patel, P., R. Christan, and J. Gardner, Investigatin f Unexpectedly L Field-Observed Fluid Mbilities during Se CO Tertiary Flds, SPE, Nv 1987, Vl., N. 4, Mungan, Necttin, Rle f Wettability and Interfacial Tensin in Water Flding, SPE, Jun 1964, Vl. 4, N., Dng, Y., B. Dindru, and C. Ishizaa, An Experiental Investigatin f Carbnated Water Flding, SPE Internatinal, Hl, L., Carbn Dixide Slvent Flding fr Increased Oil Recvery, SPE, 1959, Vl. 16, Nevers, D., Nle, A Calculatin Methd fr Carbnated Water Flding, SPE, Mar 1964, Vl. 4, N. 1, Shrabi, M., M. Riazi, and M. Jailahady, Enhanced Oil Recvery and CO Strage by Carbnated Water Injectin, IPTC, Dec Eera, M., H. Sara, A Genetic Algrith-Based Mdel t Predict CO-il Physical Prperties fr Dead and Live Oil, JCPT, Feb 008, Vl. 47, N.. 8. Duan, Z., R. Sun, An Iprved Mdel Calculating CO Slubility in Pure Water and Aqueus NaCl Slutins fr 73 t 533K and fr 0 t 000 bar, Che. Gel., 003, Vl. 193, Deruiter, R., L. Nash, and M. Singletary, Slubility and Displaceent Behavir f a Viscus Crude ith CO and Hydrcarbn Gases, SPERE, May 1994, Vl. 9, N., Kestin, J., C. Liffrd, and H. Khalifa, Viscsity f Aqueus Ptassiu Chlride Slutins in the Teperature Range and the Pressure Range 0-30 MPa, J. f Cheical and Engineering Data, 1978, Vl. 4,N., Kuar, S., S. Trabzadeh, and L. Handy, Relative Pereability Functins fr High and L Tensin Syste at Elevated Teperatures, SPE Califrnia Reginal Meeting, Mar c r