The Role Analysis of Superheated Steam Injection to Improve Performance in Thin Heavy Oil Reservoir

Transcription

1 Jurnal f Industrial and Intelligent Infrmatin Vl., N., September The Rle Analysis f Superheated Steam Injectin t Imprve Perfrmance in Thin Heavy Oil Reservir Zhanxi Pang Faculty f Petrleum Engineering, China University f Petrleum, Beijing, China pxiad@.cm Chengxiang Qi Sectin f Reservir Develpment, CNOOC Iraq Limited, Beijing, China saturated steam t develpment heavy il reservirs. Many experimental results shwed that superheated steam culd prmpt sme physical and chemical changes f minerals and fluids in heavy il reservirs t result in a large reductin f il viscsity r flw resistance.[]-[] In this article, based n the analysis f EOR mechanisms, the technlgy f numerical simulatin was emplyed t study technlgy advantages and perfrmance characteristics f cyclic superheated steam stimulatin in heavy il reservirs. Abstract Superheated steam has sme special prperties, such as high temperature but lw pressure, high quality (%), higher latent heat and larger specific vlume. In this article, numerical simulatin technlgy was emplyed t analyze perfrmance f cyclic superheated steam stimulatin in thin heavy il reservirs with different net pay, such as - m, - m and - m. By cntrasting f incremental il prductin, saving vlume f steam cnsumptin, distributin features f reservir temperature and il saturatin after injecting cnventinal wet steam, ht saturated steam and superheated steam, the technlgical advantages f cyclic superheated steam stimulatin was analyzed t develp heavy il reservirs. The results shwed that incremental il ability f superheated steam was much higher than cnventinal wet steam and ht saturated steam, but the degree f incremental il gradually became slwer when superheated degree was ver C. When the same vlume f heavy il was prduced by the three kinds f steams, superheated steam culd save steam cnsumptin. II. Superheated steam is water phase at a special state. The recvery mechanisms can be summarized as fllwing. Viscsity reductin: The viscsity f heavy il is very sensitive t temperature. High temperature largely reduces the viscsity f heavy il t result in decreasing flw resistance in reservirs.[] Therefre, viscsity reductin is the mst imprtant mechanisms during superheated steam injectin. Distillatin effect: Superheated steam is at a state f high temperature but lw pressure. Therefre, superheated steam can bviusly increase distillatin efficiency f crude il, especially heavy il.[] Thermal expansin: The thermal expansin degree f heavy il and rck minerals is larger under higher temperature and heat during superheated steam injectin.[]-[] Hydrthermal cracking: Heavy il ccur a series f chemical reactins, such as desulfurizatin, denitrgenatin, hydrgenatin. The hydrthermal cracking reactins largely decrease heavy il viscsity, reduce the cntent f sulfur, xygen and nitrgen in heavy il t imprve its flw ability in prus media.[] Plugging remval: A flushing effect frm high speed steam can effectively remve drilling fluid Index Terms superheated steam; heavy il reservir; cyclic steam stimulatin; EOR; numerical simulatin I. INTRODUCTION In the last few decades, steam injectin has been recgnized as an imprtant methd t develp heavy il reservirs.[] Current interest in steam injectin methd is tward the use f superheated steam, which presents higher temperature at the same pressure. The technlgy f superheated steam injectin has been applied in sme heavy il reservirs, such as Henan Oilfield in China and Pre-salt reservir f Kenjiyak Oilfield.[] [] Superheated steam is a kind f special steam whse temperature is abve the crrespnding saturated temperature at a given pressure. Cmpared with the cnventinal wet steam, superheated steam has sme characteristics, such as elevated temperature, high quality, lw pressure, large specific vlume and etc.[] Therefre, there are sme bvius differences between superheated steam and Manuscript received Nvember, ; revised April,. Engineering and Technlgy Publishing di:./jiii...- RECOVERY MECHANISMS

2 Jurnal f Industrial and Intelligent Infrmatin Vl., N., September pllutin near well bre. The plugging material can be prduced alng with ht il, steam and cndensate water during prductin t decrease flw resistance near well bre.[]-[] Emulsificatin flding: Light distillate f heavy il generates il-in-water emulsin r water-in-il emulsin in the frnt f steam cndensate in reservirs. [] [] The viscsity f il-in-water emulsin is larger than water and the viscsity f water-in-il is larger than il. Therefre, the flw resistance gradually increases in higher permeable frmatin t decrease steam fingering and imprve steam sweep efficiency in reservirs. III. A. Basic Parameters PRODUCTION PERFORMANCE ANALYSIS Accrding t the gelgical characteristics, such as, shallw depth, thin thickness and high viscsity, in Henan Oilfield, a series f reservir parameters were chsen fr numerical simulatin in this article. The reservir depth was m. The net pay was respectively chsen. m,. m and. m. The abslute permeability was - μm. The prsity was %. The initial il saturatin was %. The initial reservir temperature was C. In rder t simulate distillatin effect f crude il, il cmpnent was split light il, medium il and heavy il, as listed in Table I. During numerical simulatin, wet steam was injected int reservirs in the first cycle and then superheated steam was injected int reservirs frm the secnd cycle. The steam quality was chsen % fr wet steam at C. The higher quality % fr higher temperature f wet steam at C. The superheated degree was respectively chsen.,. and. C fr superheated steam at C. [] TABLE I. Cmpnents Prperties Mlal weight (kg/ml) Mass density (kg/m ) Critical pressure (MPa) Critical temperature ( C) Vlatilizable (yes r n) TYPE SIZES FOR CAMERA-READY PAPERS B. The Analysis f Oil Prductin Water Light il Medium il Heavy il yes yes yes n Accrding t the range f net pay in Henan Oilfield, thin heavy il reservir was classified three cases, such as -m, -m and - m. The incremental il ability was analyzed fr wet steam and superheated steam t cmpare the cumulative il prductin f C wet steam, C wet steam and different superheated degree f superheated steam. Fr thin heavy il reservirs with different thickness, the cumulative il prductin f superheated steam is bviusly higher than wet steam, as shwn in Fig.. The cumulative il prductin gradually increases as superheated degree r steam quality increases. Fr superheated steam injectin, the cumulative il prductin basically linearly increases as superheated degree increases. The results shw that the incremental il ability f superheated steam gradually increases as superheated degree increases, as shwn in Fig. (d). The degree f incremental il is larger fr thinner net pay, which presents superheated steam has a certain advantage in thinner heavy il reservirs. The reasn lies in higher temperature and quality f superheated steam. The temperature f il reservirs is higher during cyclic superheated steam stimulatin than cyclic wet steam stimulatin. The difference f il prductin is larger mre and mre as the stimulatin cycles increases. Meanwhile, the vlume f steam chamber is larger fr superheated steam than wet steam under reservir cnditins, which shws that the swept vlume f superheated steam is larger during injectin stage. [] Cumulative il prdutin (m ) Cumulative il prdutin (m ) Cumulative il prdutin (m ) +% +% +% +% +% +% +% +% +% (a) -m net pay (b) -m net pay (c) - m net pay ( KJ) ( KJ) ( KJ) Engineering and Technlgy Publishing

3 Jurnal f Industrial and Intelligent Infrmatin Vl., N., September. The percentage f incremental il prductin (%) -m -m >m The percentage f steam cnsumptin (%)..... ( KJ) +% +% +% (d) Incremental il percentage fr different net pay Figure. The results f incremental il ability fr different net pay C. The Analysis f Steam Saving Based n the il prductin f wet steam with quality f % at C, numerical simulatin was emplyed t study the amunt f steam injectin t achieve the same il prductin fr different steam, such as wet steam with quality f % at C, wet steam with quality f % at C, superheated steam with superheated degree f C, C and C at C. Fr - m heavy il reservirs, if the amunt f steam cnsumptin was regarded as % fr wet steam with quality f % at C, the amunt was % fr wet steam with quality f % at C, and the amunt are respectively %, % and % fr superheated steam with superheated degree f C, C and C at C (superheated steam temperature), as shwn in Fig. (a). Fig. (b) tells us that the amunt f steam saving are respectively.%,.%,.% and.% fr different steam, such as % wet steam at C, dry steam (superheated degree f C) at C, superheated steam with superheated degree f C and C at C in heavy il reservirs with net pay f - m. Fig. (c) tells us that the amunt f steam saving are respectively %, %, % and % fr different steam in heavy il reservirs with net pay abve m. Therefre, the cumulative steam injectin f cyclic wet steam stimulatin is far greater than cyclic superheated steam stimulatin at the same il prductin. The amunt f steam injectin gradually decreases with steam quality r superheated degree increases, as shwn in Fig. (d). The percentage f steam cnsumptin decreases as net pay increases, which presents that the thermal efficiency is higher fr high quality wet steam r superheated steam in heavy il reservirs with the same net pay. The percentage f steam cnsumptin (%) +% +% +% (a) -m net pay ( KJ) The percentage f steam cnsumptin (%) The percentage f saving steam cnsumptin (%) +% +% +% (b) -m net pay % +% +% (c) - m net pay -m -m >m % +% +% (d) The percentage f steam cnsumptin fr different steam Figure. The results f steam cnsumptin fr different net pay D. The Analysis f Reservir Prperties The distributins f reservir temperature are shwn in Fig.. The results shw that the heating area f superheated steam is bviusly larger than wet steam in heavy il reservir with the same net pay. Fr cyclic superheated steam simulatin, the heating area gradually increases as superheated degree increases. The heating area f dry steam is slightly lwer than superheated steam with a given superheated degree. While the superheated degree is ver C, the heating zne basically increases n lnger. It is the reasn why the cumulative il prductin slightly increases when superheated degree is ver C that there is the almst same temperature and heating area in the same reservir. The distributin f il saturatin is shwn in Fig.. Fr the same mass f steam injectin, the area f lw il saturatin is larger after injecting superheated steam than injecting wet steam. The area f lw il saturatin is slightly lwer after injecting dry steam than injectin superheated steam, as shwn in Fig.. Therefre, fr superheated steam, n the ne hand ( KJ) Engineering and Technlgy Publishing

4 Jurnal f Industrial and Intelligent Infrmatin Vl., N., September WET STEAM AND SUPERHEATED STEAM CONCLUSIONS V. The recvery mechanisms frm superheated steam injectin mainly include distillatin effect f superheated steam, il viscsity reductin due t high temperature, thermal expansin f heavy il, larger sweep area and higher displacement efficiency f superheated steam. The cumulative il prductin f cyclic superheated steam stimulatin is bviusly higher than that f cyclic wet steam stimulatin when the same mass f steam is injected int heavy il reservirs. The cumulative il prductin gradually increases as superheated degree increases, but the incremental il degree becmes lw when superheated degree is ver C. Fr the same mass f steam, heating area and steam chamber are lager after injecting superheated steam than wet steam. Meanwhile, the distillatin effect is strnger after superheated steam due t the higher temperature and the lwer pressure resulting in mre significant incremental il prductin. Under a cnditin f the same il prductin, the steam cnsumptin was lwer after injecting superheated steam than wet steam in the same heavy il reservirs. Superheated steam can carried mre heat and its specific vlume is larger, which can effectively enlarge sweep vlume and save large amunt steam injectin APPLICATIONS Large-scale cyclic wet steam stimulatin was carried ut in GQ zne f Henan Oilfield in February. Until February, the cumulative cycles f cyclic wet steam stimulatin reached in the zne. The cumulative mass f wet steam injectin was. t. The cumulative il prductin was. t. The water recvery percentage was.%. The il-steam rati was.. In August, cyclic superheated steam stimulatin was carried ut in GQ zne. It was divided int tw types that were respectively the superheated steam injectin after cyclic wet steam Engineering and Technlgy Publishing IV Figure. The distributin f il saturatin fr different steam in the same reservir C. steam at.superheated.. (superheated degree C) Oilsteam rati (t/t) Wet steam stimulatin Old layer Superheated New steam layer stimulatin Ttal Ttal Cumulative Cumulative Ttal Water number steam il well cut f injectin prductin number (%) cycles ( t) ( t) Dry steam at C (steam quality %). % wet.steam at C % wet steam at C Stage Figure. The temperature distributin fr different steam in the same - reservir TABLE II. THE COMPARISON OF DEVELOPMENT EFFECT BETWEEN Superheated steam at C (superheated degree C) % wet steam at C Dry steam at C (steam quality %) % wet steam at C stimulatin in the ld layer and the direct cyclic superheated steam stimulatin in a new il layer. At present, the cumulative cycles f cyclic superheated steam stimulatin have been up t. The cumulative cycles were in the ld il layer. The cumulative cycles were in the new il layer. The cumulative mass f superheated steam was. t after cyclic wet steam stimulatin in the ld il layer. The cumulative il prductin was. t. Cmpared with the frmer cyclic wet steam stimulatin, the il-steam rati was up t. frm. and the water cut decreased t.% frm.%, which shwed that cyclic superheated steam stimulatin bviusly imprved develpment effect f ld il layer. The develpment effect was better in the new layer than the ld layer. The il-steam rati was up t. during cyclic superheated steam stimulatin in the new layer. The results are tabulated in Table II. the larger specific vlume increases swept vlume f steam injectin, n the ther hand, the strnger distillatin effect increases il displacement efficiency in reservirs. The tw aspects can greatly imprve il recvery efficiency f heavy il reservirs. ACKNOWLEDGMENT

5 Jurnal f Industrial and Intelligent Infrmatin Vl., N., September The study was supprted by Natinal Natural Science Fundatin f China (), the Research Fund fr the Dctral Prgram f Higher Educatin () and the Science Fundatin f China University f Petrleum, Beijing (KYJJ--). REFERENCES [] C. Z. Yang and D. K. Han, Present status f EOR in the Chinese petrleum industry and its future, J. Petrl. Sci. Eng., vl., pp., July. [] Y. B. Wu, D. S. Ma, S. Q. Liu, H. Z. Wang, and X. Zha, EOR f superheated steam injectin in shallw heavy il reservir: A case study, presented at the Internatinal Oil and Gas Cnference and Exhibitin, Beijing, China, June -,. [] X. H. Wu, B. J. Dng, A. Z. Xu, Z. F. Fei, and R. F. Wang, Superheated steam huff and puff t revivify a marginal pre-salt heavy il reservir, presented at the SPE Asia Pacific Oil and Gas Cnference and Exhibitin, Brisbane, Queensland, Australia, Oct -,. [] X. H. Wu, A. Z. Xu, and H. L. Fan, An integrated evaluatin n factrs affecting the perfrmance f superheated steam huff and puff in heavy il reservirs, Petrl. Explr. Develp., vl., pp. -, Jan. [] M. B. Haghighi, S. Ayatllahi, and M. Shabaninejad, Cmparing the perfrmance and recvery mechanisms fr steam flding in heavy and light il reservirs, presented at the SPE Heavy Oil Cnference, Calgary, Alberta, Canada, June -,. [] C. H. Wu and A. Brwn, A labratry study n steam distillatin in prus media, presented at the Fall Meeting f the Sciety f Petrleum Engineers f AIME, Dallas, TX, Sept - Oct.,. [] H. F. Fan, Y. J. Liu, L. Y. Zhang, and X. F. Zha, The study n cmpsitin Changes f heavy ils during steam stimulatin prcesses, Fuel, vl., pp. -, Jan. [] G. Q. Tang, A. Inuye, V. Lee, D. Lwry, and W. Wei, Investigatin f recvery mechanism f steam injectin in heavy il carbnate reservir and mineral disslutin, presented at the SPE Western Reginal Meeting, Bakersfield, Califrnia, USA, Mar -,. [] S. Cengiz, A study f steam-water relative permeability, presented at the SPE Western Reginal Meeting, Bakersfield, Califrnia, May -,. [] A. F. Alajmi, Mdeling the il bank frmatin during steam fld, presented at the SPE Middle East Oil and Gas Shw and Cnference, Manama, Bahrain, Sep. -,. [] C. Jabbur, M. Quintard, H. Bertin, and M. Rbin, Oil recvery by steam injectin: Three-phase flw effects, J. Petrl. Sci. Eng., vl., pp. -, May. [] T. Y. Zhu, L. S. Cheng, C. B. He, Z. X. Pang, and F. J. Zhu, Calculatin mdel f n-way parameters and heating radius in a superheated steam injectin wellbre, Petrl. Explr. Develp., vl., pp. -, May. Zhanxi Pang btained a PhD () frm the Faculty f Petrleum Engineering in China University f Petrleum, Beijing. His PhD thesis Seepage Mechanisms & Applicatins f Steam (Gas) Fam Cmpund Flding is researching the EOR mechanisms f thermal fam cmpund flding and flwing characteristics f fams in prus media. Based n the basic thery f seepage mechanics, experimental researches and theretic analysis were emplyed t research int fam shearing characteristics, flwing characteristics and blcking ability f fams in prus media, flding mechanisms f fams and thermal fams, and technlgy f injectin fam anti-water-cning. He currently wrks at the Faculty f Petrleum Engineering in China University f Petrleum, Beijing. Chengxiang Qi graduated frm the China University f Gesciences in, where he studied many curses abut petrleum engineering. Then he became a petrleum engineer at Sectin f Reservir Develpment in CNOOC Iraq Limited. His expertise is in the field f reservir engineering and numerical simulatin f thermal recvery in heavy il reservirs. He has published mre than refereed jurnal papers. Engineering and Technlgy Publishing