Dynamics of Subcritical CO2/Brine Floods for Heavy-Oil Recovery

Abstract

Immiscible CO 2 flooding is an important, field-proven heavy-oil recovery method, particularly suited for thin, marginal, or otherwise poor heavy-oil reservoirs, where thermal recovery processes are likely to be uneconomical. This paper describes the dynamics of this recovery technique on the basis of experiments conducted in a scaled model. The experiments represent a medium-heavy oil (1032 mPa's at 23°C [1,032 cp at 73°F]) occurring in a shallow, thin sand. CO 2 was injected together with brine at subcritical conditions (5.5 MPa and 21 to 23°C [800 psi and 70 to 73°F]).The CO 2 and brine superficial velocities were varied from 0.18 to 2.9 mid [0.6 to 9.5 ftlD]. This broad range of velocities permitted the study of the effect of the viscous, diffusive, and gravitational forces on the CO 2 slug (20% HCPV) process for heavy-oil recovery. It was found that viscous forces completely dominated CO 2 injection. Also, the mass transfer betweeri CO 2 and oil had a stabilizing effect on the brine injection. Although the molecular diffusion of CO 2 in oil was high, it was not high enough to mobilize appreciable amounts of oil from uninvaded zones.The scaled experiment results showed that oil recoveries at CO 2 and brine breakthroughs were rate-dependent. While recovery at CO 2 breakthrough decreased with increasing rate, recovery at brine breakthrough increased. Reduction of in~erfacial tension (1FT) between brine and oil, leading to the formation of brine-in-oil emulsions, was found to be an additional effective mechanism of heavy-oil recovery by C0 2 /brine injection.

Experimental investigation of miscibility conditions of dead and live asphaltenic crude oil–CO2 systems

“…For this purpose, gas injection as an efficient enhanced oil recovery technique has been utilized to recover the remaining oil in place by reduction of the interfacial tension and viscosity and maintaining the reservoir pressure (Jha 1985;Rojas and Ali 1988). Among of the existed gases, use of the carbon dioxide (CO 2 ) is one of the proposed methods with relatively low cost and high efficiency to improve oil recovery (Ali and Thomas 1996;Alvarado and Manrique 2010;Moritis 2004).…”

Effects of Physical Parameter Range on Dimensionless Variable Sensitivity in Water Flooding Reservoirs

“…Once again, we find out that the sensitivity factors of π 17 , π 18 and π 19 increase with the injection rate. Since the pressure difference is proportional to injection rate, water, oil and rock can no longer be regarded as incompressible in high pressure environment.…”

“…From the physical point of view, π 1 , π 2 and π 3 are the permeability similarity parameters, π 4 , π 5 , π 6 , π 7 , π 8 and π 9 the similarity in geometry, π 10 and π 11 the ratios of the irreducible water and residual oil saturation to the mobile oil saturation, π 12 the reduced initial water saturation, π 14 and π 15 the ratios of the viscosity and density of water to oil, π 13 and π 16 the ratios of the capillary and gravity forces to the driving force, π 17 , π 18 and π 19 the relative volume variation ratios of oil, water and rock under the reservoir pressure, respectively. π 20 , π 21 , π 22 and π 23 denote the respective ratios of the reference pressure of oil and water, the bottom pressure of the production well, and the initial pressure to the reservoir pressure difference.…”

“…Islam et al [15] gained the scaling criteria of surfactant-enhanced alkaline/polymer multiple flooding flows. Slavash et al [16], Rojas et al [17], Erdal et al [18], Grattoni et al [19] and Ekwere [20] dealt with the similarity law for CO 2 flooding reservoir.…”

Three-dimensional physical simulation experiment study on carbon dioxide and dissolver assisted horizontal well steam stimulation in super heavy oil reservoirs

“…During the development process of super heavy oil reservoirs by chemical agent Mokrys 1991, 1993) such as dissolver and hydrocarbon solvent assisted steam, chemical agent can break the macromolecular structure of asphaltenes, decrease oil viscosity and oil-water interfacial tension, increase flowing ability of super heavy oil, and then decrease injection pressure of subsequent injected steam (Luigi et al 1994;Pradeep et al 2008). Injecting the non-condensate gas (Sun et al 2012;Khataniar et al 1999) such as nitrogen and carbon dioxide can complement the reservoir energy and enhance the carrying heat property of steam, among which, the CO 2 can dissolve in super heavy oil and decrease oil viscosity and interfacial tension, extract and gasify the light hydrocarbon in the crude oil, and increase formation elastic energy (Simon 1965;Miller and Jones 1981;Rojas and Ali 1988;Tao et al 2009). …”