EOR Using Thin Oil Film Drainage Mechanism in Water Wet Oil Reservoir

Abstract

Abstract Recovery of residual oil by gas flooding is one of the usual and effective Enhanced Oil recovery (EOR) methods. However, generally in immiscible gas flooding operation, high oil recovery cannot be expected, especially in waterflood reservoirs. In such cases, if the relationship of interfacial tensions among three phases (oil, gas and water) meets some conditions, thin oil film drainage mechanism is applicable as a unique EOR technique. Oil film drainage phenomena involve the formation of a thin film by residual oil brobs in water wet media which becomes continuous between water and gas under certain conditions and consequently recovers mobility. This investigation reports the results from experimental and mathematical model studies of the pore scale thin oil film drainage mechanism responsible for the mobilization of waterflood residual oil by immiscible gas floods in strongly water wet conditions in high pressure and high temperature conditions. One is the micro pore film flow experiment study, and another is 2 Dimensional 3 phase micro flow simulation study based on Lattice Boltzmann Method (LBM). These two approaches show that thin oil film drainage become very effective to recover water flood residual oil in the case of Positive Spreading Coefficient, especially with high positive value. The higher the positive spreading value, the more the oil recovery, because in such case, the thin oil film spreads and flows easily in the reservoir. Furthermore in order to verify oil recovery enhancement of gasflood by oil film flow in the reservoir condition (that is, high pressure and high temperature, three dimension porous space), a core flood experiment assuming film flow was carried out under the same conditions as actual reservoir. Since the oil film is supposed to be formed after the interfacial tensions are balanced, a soak period was set during gasflood to balance the interfacial tensions. The oil production behavior was different between before and after the soak period, which indicates that the film flow phenomena occurred.