− | Relating withdrawal efficiency in the air-mercury system to recovery efficiency in the hydrocarbon-water system is dependent on properties of the fluids as well as properties of the pore system. Fluid properties that affect recovery include viscosity, density, interfacial tension, [[wettability]], contact angle hysteresis, and rate of displacement (Wardlaw and<ref name=Wardlaw_etal_1978 />. Nevertheless, for a given range of fluid properties in a water wet reservoir, the same pore geometry factors that contribute to increased mercury withdrawal efficiency also increase hydrocarbon recovery efficiency. | + | Relating withdrawal efficiency in the air-mercury system to recovery efficiency in the hydrocarbon-water system is dependent on properties of the fluids as well as properties of the pore system. Fluid properties that affect recovery include viscosity, density, interfacial tension, [[wettability]], contact angle hysteresis, and rate of displacement (Wardlaw and Cassan, 1978)<ref name=Wardlaw_etal_1978 />. Nevertheless, for a given range of fluid properties in a water wet reservoir, the same pore geometry factors that contribute to increased mercury withdrawal efficiency also increase hydrocarbon recovery efficiency. |
− | Another type of mercury test involves injecting mercury to a saturation less than the maximum, withdrawing the mercury to some residual wetting phase saturation, and then reinjecting the mercury. This process, repeated several times to progressively higher maximum pressures, produces hysteresis loops. These loops, wherein mercury is partially withdrawn and then reinjected, can be used to investigate withdrawal efficiency at various initial saturations (Morrow, 1970<ref name=Morrow_1970>Morrow, N. R., 1970, Irreducible wetting phase saturations in porous media: Chemical Engineering Science, v. 25, p. 1799-1815.</ref>; Melrose and Brandner, 1974<ref name=Melrose_etal_1974>Melrose, J. C., and C. F. Brandner, 1974, Role of capillary forces in determining microscopic displacement efficiency for oil recovery by [[waterflooding]]: Journal Canadian Petroleum Technology, v. 13, p. 54-62.</ref>; Wardlaw and Taylor, 1976<ref name=Wardlaw_etal_1976>Wardlaw, N. C., and R. P. Taylor, 1976, Mercury capillary pressure curves and the interpretation of pore structures and capillary behavior in reservoir rocks: Bulletin of Canadian Petroleum Geology, v. 24, p. 225-262.</ref>; Wardlaw and Cassan, 1978<ref name=Wardlaw_etal_1978>Wardlaw, N. C., and J. P. Cassan, 1978, Estimation of recovery efficiency by visual observation of pore systems in reservoir rocks: Bulletin of Canadian Petroleum Geology, v. 26, p. 572-585.</ref>; Wardlaw et al., 1988<ref name=Wardlaw_etal_1988>Wardlaw, N. C., M. McKellar, and Y. Li, 1988, Pore and throat size distribution determined by mercury porosimetry and by direct observation: Carbonates and Evaporites, v. 3, p. 1-15.</ref>). Results suggest that the higher the initial saturation of the nonwetting phase, the greater the withdrawal efficiency. Porosimetry uses hysteresis loops to interpret pore body and pore throat size distributions and their patial arrangement (Dullien and Dhawan, 1974<ref name=Dullien_etal_1974>Dullien, F. A. L., and G. K. Dhawan, 1974, Characterization of pore structure by a combination of quantitative photomicrography and mercury porosimetry: Journal Colloid and Interface Science, v. 47, p. 337-349.</ref>; Wardlaw et al., 1988<ref name=Wardlaw_etal_1988 />). Pore sizes have also been evaluated with rate-controlled mercury injection (Yuan and<ref name=Yuan_etal_1986>Yuan, H. H., and B. F. Swanson, 1986, Resolving pore space characteristics by rate-controlled porosimetry: 5th Symposium on [[Enhanced oil recovery]] of the Society of Petroleum Engineers and the Department of Energy, April, SPE/DOE 14892, 9 p.</ref>. | + | Another type of mercury test involves injecting mercury to a saturation less than the maximum, withdrawing the mercury to some residual wetting phase saturation, and then reinjecting the mercury. This process, repeated several times to progressively higher maximum pressures, produces hysteresis loops. These loops, wherein mercury is partially withdrawn and then reinjected, can be used to investigate withdrawal efficiency at various initial saturations (Morrow, 1970<ref name=Morrow_1970>Morrow, N. R., 1970, Irreducible wetting phase saturations in porous media: Chemical Engineering Science, v. 25, p. 1799-1815.</ref>; Melrose and Brandner, 1974<ref name=Melrose_etal_1974>Melrose, J. C., and C. F. Brandner, 1974, Role of capillary forces in determining microscopic displacement efficiency for oil recovery by [[waterflooding]]: Journal Canadian Petroleum Technology, v. 13, p. 54-62.</ref>; Wardlaw and Taylor, 1976<ref name=Wardlaw_etal_1976>Wardlaw, N. C., and R. P. Taylor, 1976, Mercury capillary pressure curves and the interpretation of pore structures and capillary behavior in reservoir rocks: Bulletin of Canadian Petroleum Geology, v. 24, p. 225-262.</ref>; Wardlaw and Cassan, 1978<ref name=Wardlaw_etal_1978>Wardlaw, N. C., and J. P. Cassan, 1978, Estimation of recovery efficiency by visual observation of pore systems in reservoir rocks: Bulletin of Canadian Petroleum Geology, v. 26, p. 572-585.</ref>; Wardlaw et al., 1988<ref name=Wardlaw_etal_1988>Wardlaw, N. C., M. McKellar, and Y. Li, 1988, Pore and throat size distribution determined by mercury porosimetry and by direct observation: Carbonates and Evaporites, v. 3, p. 1-15.</ref>). Results suggest that the higher the initial saturation of the nonwetting phase, the greater the withdrawal efficiency. Porosimetry uses hysteresis loops to interpret pore body and pore throat size distributions and their patial arrangement (Dullien and Dhawan, 1974<ref name=Dullien_etal_1974>Dullien, F. A. L., and G. K. Dhawan, 1974, Characterization of pore structure by a combination of quantitative photomicrography and mercury porosimetry: Journal Colloid and Interface Science, v. 47, p. 337-349.</ref>; Wardlaw et al., 1988<ref name=Wardlaw_etal_1988 />). Pore sizes have also been evaluated with rate-controlled mercury injection (Yuan and Swanson, 1986)<ref name=Yuan_etal_1986>Yuan, H. H., and B. F. Swanson, 1986, Resolving pore space characteristics by rate-controlled porosimetry: 5th Symposium on [[Enhanced oil recovery]] of the Society of Petroleum Engineers and the Department of Energy, April, SPE/DOE 14892, 9 p.</ref>. |