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ABSTRACTWater Alternating Gas injection (WAG) or Simultaneous Water and Gas Injection (SWAG) floods have been proposed as very good solution to overcome gravity segregation and better EOR performance in compare to conventional continuous gas injection (CGI). However WAGBased processes cause some problems associated with increased water saturation including diminished gas injectivity. As an effective alternative for WAG, Gas Assisted Gravity Drainage (GAGD) for conventional reservoirs has been developed (US Patent 20060289157) that takes advantage of the natural segregation of gas from liquid hydrocarbon during injection. The GAGD process consists of placing a horizontal producer near the bottom of oil column and injecting gas through existing vertical wells. As the injected gas rises to form a gas zone, oil and water drain down to the horizontal producer. Application of GAGD for IOR in naturally fractured reservoir is discussed here based on some facts and figures.
IPTC 13244 Gas-Assisted Gravity Drainage (GAGD) Process for Improved Oil Recovery Norollah Kasiri and A Bashiri, Iran University of Science & Technology Copyright 2009, International Petroleum Technology Conference This paper was prepared for presentation at the International Petroleum Technology Conference held in Doha, Qatar, 7–9 December 2009 This paper was selected for presentation by an IPTC Programme Committee following review of information contained in an abstract submitted by the author(s) Contents of the paper, as presented, have not been reviewed by the International Petroleum Technology Conference and are subject to correction by the author(s) The material, as presented, does not necessarily reflect any position of the International Petroleum Technology Conference, its officers, or members Papers presented at IPTC are subject to publication review by Sponsor Society Committees of IPTC Electronic reproduction, distribution, or storage of any part of this paper for commercial purposes without the written consent of the International Petroleum Technology Conference is prohibited Permission to reproduce in print is restricted to an abstract of not more than 300 words; illustrations may not be copied The abstract must contain conspicuous acknowledgment of where and by whom the paper was presented Write Librarian, IPTC, P.O Box 833836, Richardson, TX 75083-3836, U.S.A., fax +1-972-952-9435 ABSTRACT Water Alternating Gas injection (WAG) or Simultaneous Water and Gas Injection (SWAG) floods have been proposed as very good solution to overcome gravity segregation and better EOR performance in compare to conventional continuous gas injection (CGI) However WAG-Based processes cause some problems associated with increased water saturation including diminished gas injectivity As an effective alternative for WAG, Gas Assisted Gravity Drainage (GAGD) for conventional reservoirs has been developed (US Patent 2006/0289157) that takes advantage of the natural segregation of gas from liquid hydrocarbon during injection The GAGD process consists of placing a horizontal producer near the bottom of oil column and injecting gas through existing vertical wells As the injected gas rises to form a gas zone, oil and water drain down to the horizontal producer Application of GAGD for IOR in naturally fractured reservoir is discussed here based on some facts and figures Xen kẽ nước Gas injection (WAG) đồng thời nước Gas Injection (SWAG) lũ lụt đề xuất giải pháp tốt để vượt qua lực hấp dẫn phân biệt hiệu suất tốt EOR so sánh với phun khí liên tục thông thường (CGI) Tuy nhiên trình WAG-Dựa gây số vấn đề liên quan với tăng độ bão hòa nước bao gồm injectivity khí giảm Là thay hiệu cho WAG, Gas Assisted Trọng lực thoát nước (GAGD) cho hồ chứa thông thường phát triển (US Patent 2006/0289157) mà lợi dụng phân biệt tự nhiên khí hydrocarbon lỏng từ tiêm Quá trình GAGD bao gồm việc đặt nhà sản xuất ngang gần phía cột dầu bơm khí đốt qua giếng thẳng đứng Khi khí bơm tăng để tạo thành khu vực khí đốt, dầu mỏ thoát nước xuống cho nhà sản xuất ngang Áp dụng cho GAGD IOR hồ chứa tự nhiên bị gãy thảo luận dựa số kiện số KEYWORDS: Gravity Drainage, Improved Oil Recovery, Fractured Reservoir, Simulation INTRODUCTION Worldwide EOR surveys by the Oil and Gas Journal (April 21, 2008) for the last two decades clearly shows increased popularity and production share of gas injection processes in the world Review of related experiences indicates that sweep & microscopic displacement efficiency are major issues for any successful EOR Process Microscopic efficiency (as extent of mobilizing the trapped reservoir residual oil) is a function of capillary number (Ca) as ratio of viscous to capillary forces On the other hand, the volumetric sweep, defined as the percentage of reservoirs contacted by the injected fluid, is governed by the mobility ratio and reservoir heterogeneity (Willhite et al., 1998): Các điều tra toàn giới EOR Dầu Gas Journal (ngày 21 tháng tư năm 2008) hai thập kỷ qua cho thấy rõ ràng tăng phổ biến sản xuất phần trình phun khí giới Tổng kết kinh nghiệm liên quan cho thấy quét & hiệu chuyển vi vấn đề lớn trình EOR thành công Hiệu vi (như mức độ huy động hồ chứa bị bẫy dầu dư) chức số lượng mao mạch (Ca) tỷ lệ nhớt để lực mao dẫn Mặt khác, quét thể tích, định nghĩa tỷ lệ phần trăm hồ chứa liên lạc với chất lỏng tiêm, điều chỉnh tỷ lệ di động hồ chứa không đồng (Willhite et al., 1998): µDνD Ca = σ λD M= λd λkl= l µl (1) (2) (3) IPTC 13244 To maximize efficiency of any EOR process, the capillary number should be maximized while minimizing the mobility ratio Gas injection EOR processes are excellent in microscopic displacement efficiencies due to small interfacial tension developed between the injected gas and reservoir oil, which can be further decreased to zero during miscible injection that boosts Capillary Number value But volumetric sweep efficiency of these EOR processes is their major shortcoming (Satter et al., 2008) Viscosity of commonly injected gases such as carbon dioxide and hydrocarbons is about one-tenth of the reservoir fluids viscosities that will cause unfavorable mobility ratios and severe gas-oil gravity segregation with large un-swept reservoir areas Fortunately some forecasting tools such as viscous gravity number can be used to evaluate this issue (Green et al., 2000) In order to improve sweep efficiency of Gas Injection Water Alternating Gas (WAG) has been widely practiced with simultaneous decrease for injection gas requirements Although conceptually sound, the WAG process has not measured up to expectations as evidenced by the low (5–10%) recoveries observed in 59 field applications (Kulkarni et al., 2006) Imperfect mobility ratio improvements and increased mobile water saturation that causes water shielding (the water films prevent oil and gas coming into direct contact and, for miscible gas injection, delay the onset of miscibility) can justify this poor recovery within WAG Process The drainage of oil under gravity forces, either through gas cap expansion or by gas injection at the crest of the reservoir, has proven to be an efficient gas injection method (with considerable corefloods and filed investigation) since it can reduce the residual oil saturation to very low values Recoveries as high as 85–95% OOIP (Original Oil in Place) have been reported in field tests and nearly 100% recovery efficiencies have been observed in laboratory floods (Ren, 2002) Gravity stable gas injection takes advantage of the density difference between injected gas and reservoir fluid that cause problems of poor sweep efficiencies and gravity override in horizontal gas floods (such as WAG) This concept has been used in next sections to introduce interesting EOR process within naturally fractured reservoir Để tối đa hóa hiệu trình EOR, số mao mạch nên tối đa giảm thiểu tỷ lệ di động Quy trình EOR phun khí tuyệt vời hiệu suất chuyển vi căng bề nhỏ phát triển khí tiêm dầu chứa, mà giảm để không tiêm trộn làm tăng mao Số giá trị Nhưng hiệu quét thể tích trình EOR thiếu sót lớn họ (Satter et al, 2008.) Độ nhớt chất khí thường tiêm carbon dioxide hydrocarbon khoảng phần mười chất lỏng chứa nhớt mà gây tỷ lệ di động không thuận lợi khí dầu trọng lực phân biệt nghiêm trọng với khu vực hồ chứa un-quét lớn May mắn thay số công cụ dự báo số trọng lực nhớt sử dụng để đánh giá vấn đề (Green et al., 2000) Để nâng cao hiệu quét khí phun nước Xen kẽ Gas (WAG) thực rộng rãi với mức giảm đồng thời cho yêu cầu khí tiêm Mặc dù khái niệm âm thanh, trình WAG không đo theo mong đợi chứng (510%) phục hồi thấp quan sát 59 lĩnh vực ứng dụng (Kulkarni et al., 2006) Cải thiện tỷ lệ di động không hoàn hảo tăng độ bão hòa nước di động có gây che chắn nước (các phim nước ngăn chặn dầu khí tiếp xúc trực tiếp dùng để tiêm khí trộn lẫn, trì hoãn khởi hòa trộn) biện minh cho việc phục hồi vòng WAG Process Hệ thống thoát nước dầu thuộc lực lượng trọng lực, thông qua việc mở rộng nắp xăng phun khí đỉnh hồ chứa, chứng minh phương pháp phun khí hiệu (với corefloods đáng kể nộp tra) làm giảm độ bão hòa dầu dư để giá trị thấp Phục hồi cao 85-95% OOIP (Original Oil in Place) báo cáo thử nghiệm lĩnh vực gần 100% hiệu phục hồi quan sát thấy lũ lụt phòng thí nghiệm (Ren, 2002) Trọng lực phun khí ổn định lợi dụng chênh lệch mật độ khí chất lỏng tiêm chứa gây vấn đề hiệu suất quét nghèo trọng lực đè lũ khí ngang IPTC 13244 (như WAG) Khái niệm sử dụng phần để giới thiệu trình EOR thú vị hồ chứa tự nhiên bị gãy GAS–OIL GRAVITY DRAINAGE (GOG D) IN NFR In naturally fractured reservoirs (NFR), the matrix which contains most of the oil is surrounded by a system of fractures of very little volume but with permeabilities that are several orders of magnitude higher than that of the matrix (not for all type of Fractured Reservoirs but Type II which is encountered in south of Iran frequently): Trong vỉa bị nứt tự nhiên (NFR)các khối, có hầu hết lượng dầu bao quanh hệ thống gãy xương thề tích với độ thấm số đơn đặt hàng cường độ cao so với ma trận (không phải cho tất loại hồ chứa bị vỡ Type II gặp phải phía nam Iran thường xuyên): Table1: Classification of Naturally Fractured Reservoir (Nar et al., 2006) NFR TYPE TYPE1 DEFINITION Fractures provide essential porosity and permeability TYPE2 Fractures provide essential permeability TYPE3 Fractures provide a permeability assistance EXAMPLES Amal, Libya Edison, California Agha Jari, Iran Haft kel, Iran Spraberry Trend Area, Texas Kirkuk, Iraq Dukhan,Quatar In such reservoir it is difficult to apply pressure differential in the matrix to recover its oil content by conventional displacement process because injected fluid simply flows through the fracture system bypassing the oil in the matrix However by introduction of gas into the fracture system such that the gas-oil contact (GOC) in the fracture system becomes deeper than the GOC in the matrix, then a hydrostatic imbalance is created The oil in the matrix above the fracture GOC is surrounded by gas and is forced to drain downwards by virtue of its higher density ultimately into the fracture oil rim As the oil drains from the matrix it is replaced by gas and the oil collecting in the fracture system can then be produced This process is called gas-oil gravity drainage (GOGD) Figure1 shows mathematical framework for gravity drainage from single block within a given fractured reservoir Van Golf-Racht (1982) showed that gravity drainage displacement of oil by gas will start only if the column of gas in the fracture (Hg) is higher than the threshold height because in such displacement the capillary pressure has a negative effect on production and oil can be produced to the extent that gravitational forces exceed capillary forces The gravity segregation in a given naturally fractured reservoir is highly affected by extent of capillary continuity between matrix blocks across fractures, and by the process of oil reinfiltration from fractures to matrix blocks (Kleppe, 1996): Trong hồ chứa vậy, khó để áp dụng chênh lệch áp suất ma trận để khôi phục lại nội dung dầu trình chuyển thông thường chất lỏng tiêm đơn giản chảy qua hệ thống đứt gãy bỏ qua dầu ma trận Tuy nhiên theo giới thiệu khí vào hệ thống đứt gãy mà liên lạc khí-dầu (GOC) hệ thống đứt gãy trở nên sâu sắc so với GOC ma trận, sau cân thủy tĩnh tạo Dầu ma trận chỗ gãy GOC bao quanh khí buộc phải thoát xuống nhờ mật độ cao cuối vào rim dầu gãy xương Như IPTC 13244 cống rãnh dầu từ ma trận thay khí dầu thu thập hệ thống đứt gãy sau sản xuất Quá trình gọi hệ thống thoát nước trọng lực khí-dầu (GOGD) Hình lãm khuôn khổ toán học cho hệ thống thoát nước trọng lực từ khối hồ chứa bị vỡ Văn Golf-Racht (1982) cho thấy thuyên thoát nghiêm trọng dầu khí bắt đầu cột khí gãy xương (Hg) cao so với chiều cao ngưỡng thuyên áp lực mao mạch có ảnh hưởng tiêu cực đến sản xuất dầu sản xuất đến mức lực hấp dẫn lực mao dẫn Sự phân biệt trọng lực hồ chứa bị nứt tự nhiên cho ảnh hưởng mạnh mẽ mức độ mao mạch liên tục khối ma trận gãy xương, trình xâm nhập ngược dầu từ gãy xương cho khối ma trận (Kleppe, 1996): Fig.1 Oil Displacement by Gas oil Gravity Drainage within Matrix Block of Fractured Reservoir One of the very important issues in studying a given naturally fractured reservoir, regardless of simulation model capabilities, is to investigate the presence and the degree of capillary continuity within reservoir structure (Refer to Fig for different possible fracture-matrix interaction) Some authors are advocating the presence of capillary continuity (BlockBlock Interaction) in fractured reservoir but their conclusion is mainly based on the results of superficial and simple laboratory experiments or simulation observations (Saidi, 2006) which is not valid for actual reservoir simulation studies Một vấn đề quan trọng việc nghiên cứu hồ chứa bị nứt tự nhiên định, khả mô hình mô phỏng, để điều tra diện mức độ mao mạch liên tục cấu trúc chứa (Tham khảo Hình cho khác tương tác gãy-matrix) Một số tác giả ủng hộ diện mao mạch liên tục (Block-Block Interaction) hồ chứa bị vỡ kết luận họ chủ yếu dựa kết thí nghiệm phòng thí nghiệm hời hợt đơn giản quan sát mô (Saidi, 2006) không hợp lệ cho nghiên cứu mô hồ thực tế Fig.2 Schematic Representation of Different Types of Matrix-Fracture Interaction (Saidi, 1987) For example if fair to good capillary continuity exists between blocks, repressurizing a fractured reservoir by gas injection would mainly give the swelling benefit of the residual oil saturation Whereas if poor capillary continuity exists in a reservoir, gas repressurizing will considerably improve oil recovery throughout both swelling and reducing interfacial tension and thus the threshold height of matrix The presence and degree of capillary continuity can be estimated by analyzing the variation of oil production rate versus the variation of oil column thickness or the variation of gas-oil contact within a given reservoir (Saidi, 1987) Also if the horizontal fractures are partially filled with impermeable materials then a poor capillary continuity should be expected Therefore confirmation of capillary continuity (and its extent) within a given fracture reservoir is more important than its mathematical modeling An important aspect in gas-oil gravity drainage of fractured reservoirs (with direct impact on gravity drainage and EOR processes such as gas assisted gravity drainage) is reinfiltration process when drained oil from an upper matrix block enters (totally or partially) into lower one (Fig.2) The flow from one block to another (reinfiltration) is either achieved by film flow across contact points or by liquid bridges The reinfiltration mechanism is also time dependent, since liquid bridging provides the main transmissibility in the initial stage of the gravity drainage process Later the oil saturation in the fractures will be very low and the main liquid transmissibility from block to block is due to film flow This final period is of long duration and is very important for the overall recovery Therefore EOR process in NFR such as Gas Assisted Gravity Drainage (GAGD) that refers to gravity drainage as main recovery mechanism should pay attention to mathematical modeling of these complex reservoirs 3 GAS ASSISTED GRAVITY DRAINAGE IN NATURALLY FRACTURED RESERVOIR The newly proposed Gas Assisted Gravity Drainage (GAGD) process (Rao et al., 2008) provide a process which extrapolates the highly successful gravity stable gas injection processes The GAGD process consists of placing a horizontal producer at the bottom of the pay zone and injecting gas through existing vertical wells at the top (into the gas cap) to provide gravity stable displacement and uniform reservoir sweep This process takes advantage of the gravity segregation effects and horizontal wells technology for different types of reservoirs Horizontal wells have the advantage of having a high productivity index (due to large contact with the reservoir) Furthermore, horizontal wells are ideal for the gravity drainage processes (Rao et al, 2004) The main advantage of placing the horizontal well at the bottom of the pay zone in GAGD is that when the natural drive of oil such as gas cap or solution drive has been depleted, gravity forces will take over with continued oil production A second advantage of horizontal wells is that they able to delay gas breakthrough and the encroachment of water: Các khí đề xuất hỗ trợ trọng lực thoát nước (GAGD) trình (Rao et al., 2008) cung cấp trình mà extrapolates trọng lực ổn định trình phun khí thành công Quá trình GAGD bao gồm việc đặt nhà sản xuất ngang phía vùng lương tiêm chích khí thông qua giếng thẳng đứng đầu (vào nắp gas) để cung cấp cho lực hấp dẫn di dời ổn định thống quét hồ chứa Quá trình lợi hiệu ứng trọng lực phân biệt giếng ngang công nghệ với nhiều loại khác hồ chứa Giếng ngang có lợi việc có số suất cao (do tiếp xúc lớn với hồ chứa) Hơn nữa, giếng ngang lý tưởng cho trình thoát nước trọng lực (Rao et al, 2004) Ưu điểm việc đặt ngang phía vùng lương GAGD ổ đĩa tự nhiên dầu nắp xăng ổ đĩa giải pháp bị cạn kiệt, lực lượng trọng lực qua với sản lượng dầu tiếp Một lợi thứ hai giếng ngang họ trì hoãn đột phá khí xâm lấn nước: Fig 3: Schematic of Gas Assisted Gravity Drainage Process (US Patent 2006/0289157) The only published experimental data (immiscible Injection) related to GAGD within a simple fractured core with only two vertical fractures (Mahmoud et al., 2007) have been checked here with an in-house numerical code for fractured reservoir simulation Due to nature of the code which is developed for well-fractured reservoir and estimation of some data that was not reported for mentioned fractured core it is interesting that good agreement is available between predicted and actual data Regardless of simulation results and refer to experimental trend within this example (Fig 4) and importance of gas-oil gravity drainage within NFR as major recovery mechanism it can be stated that GAGD should be considered as competitive IOR candidate for naturally fractured reservoir with deep oil column Kulkarni et al (2006) introduced a new dimensionless group as "gravity Drainage Number" with corresponding approximate correlations for GAGD oil recovery (miscible and immiscible) based on some 2D physical model, 1D Core Floods and 3D Filed data: Các liệu thực nghiệm công bố (tiêm immiscible) liên quan đến GAGD lõi gãy đơn giản với hai vết nứt thẳng đứng (Mahmoud et al., 2007) kiểm tra với mã số nhà cho mô hồ chứa bị vỡ Do tính chất mã phát triển cho hồ chứa bị gãy ước số liệu không báo cáo cho đề cập lõi gãy thú vị thỏa thuận tốt có sẵn liệu dự đoán thực tế Bất kể kết mô tham khảo xu hướng thử nghiệm ví dụ (Hình 4) tầm quan trọng hệ thống thoát nước trọng lực khí-dầu NFR chế thu hồi lớn khẳng định GAGD nên coi cạnh tranh ứng cử viên IOR cho hồ chứa tự nhiên bị gãy với sâu cột dầu Kulkarni et al (2006) giới thiệu nhóm thứ nguyên "lực hấp dẫn thoát nước Number" với tương quan tương ứng để thu hồi dầu GAGD (có thể trộn immiscible) dựa số mô hình vật lý 2D, 1D lõi Lũ lụt 3D Nộp liệu: q (N¢ + NB)] g +N[GD = NG o q (4) Where NB (Bond Number) measures the relative strength of gravity and capillary forces and NG is a combination of the bond & capillary number Structure of NGD indicate that k (absolute permeability) is solely source of difference for NGD value between fractured and conventional reservoirs In this basis and because fractured reservoir can have higher absolute permeability than conventional one (generally), experimental data in Fig become reasonable Also refer to approximate correlations (Equation & 8) and definition of gravity drainage number it can be said that miscible GAGD can yield better overall recovery in fractured reservoir due to small interfacial tension (near zero) developed between injected gas and reservoir fluid in this condition that boosts Capillary Number and Bond Number values Nơi NB (Bond Number) đo sức mạnh tương đối trọng lực lực lượng mao mạch NG kết hợp số trái phiếu mao mạch Cấu trúc NGD k (độ thấm tuyệt đối) nguồn gốc khác biệt cho NGD giá trị hồ chứa bị vỡ thông thường Trong sở hồ chứa bị vỡ có độ thấm tuyệt đối cao so với quy ước (nói chung), liệu thử nghiệm hình trở nên hợp lý Cũng đề cập đến mối tương quan gần (Equation7 & 8) định nghĩa số lượng thoát nước trọng lực nói GAGD thể trộn mang lại phục hồi tổng thể tốt hồ chứa bị vỡ căng thẳng nhỏ bề (gần không) phát triển hệ khí tiêm chất lỏng chứa điều kiện mao mạch làm tăng số lượng Bond Số giá trị NB = NG = Δqg k ( ) $ oog (5) k Δqg ( ) $ µor (6) d Rimmiscib1e (%) = 4.59 ln(NGD) + 32.3 (7) Rmiscib1e (%) = 4.57 ln(NGD) + 55.39 (8) 100 90 80 Rec % 70 Fra ctured Core Experimental Fra ctured Core Simulati on Unfra ctured Core 60 50 20 40 10 30 0 50 100150200 Recovery, 250 300 Fig 4: Numerical and Experimental Prediction of GAGD within a simple fractured core (Core Data from Mahmoud et al., 2007) CONCLUSION Application of Gas Assisted Gravity Drainage (GAGD) within Naturally Fractured Reservoirs (NFR) has been discussed in this paper It can be stated that miscible GAGD process within a given fractured reservoir should offer better recovery in compare to immiscible one but relative density of injection gas and reservoir fluid is another issue that should be treated carefully during injection gas selection Ứng dụng khí hỗ trợ trọng lực thoát nước (GAGD) hồ chứa tự nhiên bị gãy (NFR) thảo luận viết Có thể nói trình GAGD thể trộn lẫn hồ chứa bị vỡ cung cấp phục hồi tốt so sánh với immiscible mật độ tương đối khí phun chất lỏng chứa vấn đề khác cần điều trị cẩn thận trình lựa chọn gas tiêm NOMENCLATURE Ca: Capillary Number λD: Mobility of the displacing fluid phase λd: Mobility of the displaced fluid phase λl: Mobility of the fluid kl : Effective Permeability of Phase l, mD µl: Visocity of Phase l, Pas sec σ: Interfacial Tention, N/m ν: Darcy Velocity, m/sec M: Mobility Ratio, Dimensionless µD: Displacing Fluid Viscosity, Pas Sec REFERENCES Christensen, J R., Stenby, E H., Skauge, A., 2001.Review of the WAG field experience, SPE Reservoir Evaluation & Engineering 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Canada, 2002 Saidi, A.M., 2006 Status of Dual Porosity Reservoir simulation and expected features of a new rigorous model, Technical Presentation, Petroleum Engineering and Development Company, Tehran-Iran Saidi, A.M., 1987 Reservoir Engineering of Fractured Reservoirs, TOTAL Edition press, 864 pp Satter, A., Bushwalter, J.L., Lgbal, G.M., 2008.Practical Enhanced Reservoir Engineering: Assisted with Simulation Software, PennWell Corporation, Tulsa, Oklahoma, USA, 706 pp Van Golf-Racht, T.D., 1982.Fundamentals of Fractured Reservoir Engineering, Elsevier Scientific Publishing Company, New York, USA, 710 pp [...]... Gas- Assisted Gravity Drainage EOR Process, SPE 113424, SPE/DOE Symposium on Improved Oil Recovery, Oklahoma, USA Rao, D N., Ayirala, S C., Kulkarni, M.M., Sharma, A P., 2004.Development of the Gas Assisted Gravity Drainage (GAGD) Process for Improved Light Oil Recovery , SPE 89357, SPE/DOE Fourteenth Symposium on Improved Oil Recovery, Tulsa, Oklahoma, USA Ren, W., 2002.Application of the Gravity Assisted. .. Performance Demonstration of the Gas- Assisted Gravity Drainage Process Using Visual Models, SPE 110132, SPE Annual Technology Conference and Exhibition, California, USA Narr, W., Schechter, D.W., Thompson, L.B., 2006.Naturally Fractured Reservoir Characterization, Society of Petroleum Engineers, Texas, USA, 112 pp Rao, D.N., Sharma, A.P., 2008 Scaled Physical Model Experiments to Characterize the Gas- Assisted. .. Green, D.W., Willhite, G.P., 1998.Enhanced Oil Recovery, SPE, Texas, USA, 545 pp Kleppe, J., Uleberg, K., 1996 Dual Porosity, Dual Permeability Formulation for Fractured Reservoir Simulation, Norwegian University of Science and Technology (NTNU), Trondheim RUTH Seminar, Stavanger Kulkarni, M M., Rao, D.N., 2006 Characterization of Operative Mechanisms in Gravity Drainage Field Projects through Dimensional... Mitigate Miscible Solvent Gravity Override in the Virginal Hills Margin, Journal of Canadian Petroleum Technology, Vol 39, No.2: 28-34 Fung, L.S-K., 1991.Simulation of Block-to-Block Processes in Naturally Fractured Reservoirs", SPE Reservoir Engineering, Vol 6, No 4: 477-484 Fung, L.S-K, 1993.Numerical Simulation of Naturally Fractured Reservoirs, SPE 25616, Middle East Oil Show, Society of Petroleum... (GAGD) Process for Improved Light Oil Recovery , SPE 89357, SPE/DOE Fourteenth Symposium on Improved Oil Recovery, Tulsa, Oklahoma, USA Ren, W., 2002.Application of the Gravity Assisted Tertiary Gas Injection Process, M.Sc Thesis, University of Alberta, Edmonton, Canada, 2002 Saidi, A.M., 2006 Status of Dual Porosity Reservoir simulation and expected features of a new rigorous model, Technical Presentation,... Company, Tehran-Iran Saidi, A.M., 1987 Reservoir Engineering of Fractured Reservoirs, TOTAL Edition press, 864 pp Satter, A., Bushwalter, J.L., Lgbal, G.M., 2008.Practical Enhanced Reservoir Engineering: Assisted with Simulation Software, PennWell Corporation, Tulsa, Oklahoma, USA, 706 pp Van Golf-Racht, T.D., 1982.Fundamentals of Fractured Reservoir Engineering, Elsevier Scientific Publishing Company,