XIAO Pufu, YANG Zhengming, WANG Xuewu, JIANG Baicai, LIU Guozhong
The physical simulation of the core of Daqing peripheral extra/ultra-low permeability reservoirs is designed, combined with the nuclear magnetic resonance (NMR), in consideration of four kinds of gas injection modes, that is, water injection converting to gas injection, CO2 miscible flooding, CO2 immiscible gas injection and the cycle gas injection, to study the oil displacement efficiency and the residual oil distribution of different levels permeability cores, for the development of the pilot area of Daqing CO2 pilot test area. Results indicate that, under the same conditions, the effect of the conventional water injection is the worst, but after converting to the gas injection, a larger ascension may be achieved. For extra low permeability cores, the cycle gas injection displacement efficiency is the highest. For ultra-low permeability cores, the effect of the water transfer gas is higher than that of other three modes. The residual oil distribution shows that, for the water transfer gas, the CO2 miscible flooding and the immiscible CO2 flooding, with a main use of oil in the large-medium pore, the crude oil in clay micro pore is hard to drive, but during the time of the cycle gas injection process, under the action of capillary force and the elastic energy, the crude oil flows from the micro pore to the large-medium pore, thus increasing the utilization of crude oil in small pores.
