Experimental Study and Modeling of Gravity Drainage during WAG Process in Fractured Carbonate Rocks

Document Type: Research Article


1 Department of Chemical and Petroleum Engineering, Sharif University of Technology, Tehran, I.R. IRAN

2 Arvandan Company, National Iranian Oil Company,Tehran, I.R. IRAN


The experimental study and modeling of gravity drainage during Water Alternative Gas Injection, WAG process, in carbonate rock for one of the Iranian off-shore reservoir at lab-scale were carried out. The mechanism of gravity drainage during the WAG process, and its contribution to the oil recovery in the fractured carbonate reservoirs were also studied. In the WAG process alternatively gas is injected during the process and gravity drainage could be happened. Changes in the block dimensions, rock properties, oil properties, gas properties, and fractures properties and their effect on the amount of oil recovered during the gravity drainage mechanism were studied. It would be worth mentioning that Methane, as major constituent of natural gas, was used as injection fluids within the experiments. Also carbonate rock was used as block sample in the physical model within the experiments. The results obtained from the experiments were compared with those obtained from the simulation and the comparison confirmed fair agreement between the results. It was found out that from 1 to 6 percent of oil can be recovered by gravity drainage during WAG process.


Main Subjects

[1] Halbouty, M.T., The Future of the Domestic Oil and Gas Industry, Journal of Petroleum Technology, 149(1969).
[2] Aguilera, R., Advances in the Study of Naturally Fractured Reservoirs, The Journal of Canadian Petroleum Technology, 32 (5), (1993).
[3] Saidi, A.M., “Simulation of Naturally Fractured Reservoirs”, Paper SPE 12270 Presented at the SPE Symposium on Reservoir Simulation, San Francisco, November 16-18 (1983).
[4] Hagoort, J., “Oil Recovery by Gravity Drainage”, Paper SPE 7424, SPE Journal, p. 139 (1978).
[5] Babadagli, T., Ershaghi, I., Improved Modelling of Oil/Water Flow in Naturally Fractured Reservoirs Using Effective Fracture Relative Permeabilities, SPE 26076,Presented at the SPE Western Regional Meeting, Anchorage, May 26-28, Richardson, TX: Society of Petroleum Engineers (1993).
[6] Barenblatt, G.E., Zheltov, I.P. and Kochina, I.N., Basic Concepts in the Theory of Seepage of Homogeneous Liquids in Fissured Rocks, J. Appl. Math. and Mech., p. 1286 (1960).
[7] Kazemi, H., Merrill, L.S., Porterfield, JR, K.L. and Zeman, P.R., Numerical Simulation of Water-oil Flow in Naturally Fractured Reservoirs, Society of Petroleum Engineers J., December, Trans., AIME, 261, p. 317(1976).
[8] Rossen, R.H., Shen, E.I., Simulation of Gas/Oil Drainage and Water/Oil Imbibition in Naturally Fractured Reservoirs, Paper SPE 16982 Presented
at the SPE Annual Technical Conference and Exhibition, Dallas, TX, September 27-30 (1987).
[9] Reiss, L.H, “The Reservoir Engineering Aspects
of Fractured Formations”, Gulf Publishing Co., Houston 108 (1980).
[10] Van Golf-Racht, T.D, “Fundamentals of Fractured Reservoir Engineering”, Elsevier/North Holland Inc., New York City, p. 710 (1982).
[11] Saidi, A.M., Fracture Reservoir Engineering, Total Edition Press, (1987).
[12] Higgings, R.V., Shea, G.B., Laboratory Studies of Gravitational Drainage of Oil from Unconsolidated Sands, U.S. Bureau of Mines, RI 4391(1949).
[13] Firoozabadi,  A. and  Pooladi-Dravish, M., Experi-mental and Modeling of Water Injection in Water-wet Fracturd Porous Media, journal of Canadian Petroleum Technology, (2000).
[14] Firoozabadi, A. and Hauge, J., “Capillary Pressure in Fractured Porous Media”, Journal of Petroleum Technology, pp. 784-791, (1990).
[15] Firoozabadi, A., “Aurthor’s Reply to Discussion of Capillary Pressure in Fractured Porous Media”,
SPE 22212, (1991).
[16] CHatzis, I., Kantzas, A., Dullien, F. A. L., “On the Investigation of Gravity Assisted Inert Gas Injection Using Micro Models, Long Berea Cores and Computer Assisted Tomography”, SPE 18284, Presented at the 63rd Annual Technical Conference and Exhibition of the Society of Petroleum Engineers, Held in Houston, TX, Oct, 2-5 (1988).
[17] Dyes, A. B., Kemp, C. E. and Caude, B. H., Effcçt of Fractures on Swap -out Pattern, Paper Presented at the 3rd Biennial Sccondary Recovery Symposium, Wichita Falls, Tex., May 5-6, (1958).
[18] Mattax, C. and Kyte J. R., Imbibition Oil Recovery from Fractured, Water-Drive Reservoir, SPE J.,177 (1962).
[19] Mattax,  Calvin  C.,  Kyte,  J. R.,  Imbibition  Oil Recovery from Fractured, Water Drive Reservoir, Societyof PetroleumEngineers J., p. 177 (1962).
[20] Rangel-German  E.,  Akin  S.  and  Castanier  L.,  Muiiphase-Flow Properties of Fractured Porous Media, Paper SPE 54591 Presented at the 1999 SPE Western Regional Meeting, Anchorage, Alaska, May 26-28, (1999).
[21] Horie,  Tadashi,  Firoozabadi,   A.,  “Capillary Continuity in Fractured Reservoirs”, Paper SPE 18282, (1988).
[22] Skjoeveland, S. M.,   SPOR    Monograph,    Recent Advances in Improved Oil Recovery Methods for North Sea Sandstone Reservoirs, First Printing, Norwegian Petroleum Directorate, Stavanger (1992).
[23] Surguchev, L.M. et. al. Screening of WAG Injection Strategies for Heterogeneous Reservoirs, Paper
SPE- 25075, Presented at European Petroleum Conference, France (1992).
[24] Skauge, A.,  Simulation  studies  of  WAG  using Three-phase Relative Permeability Hysteresis Models, 9th European Symposium on IOR, The Hague, Oct., (1997).