选取大庆外围特/超低渗透储层岩心进行物理模拟实验,结合核磁共振,通过注水转注气、CO2混相驱、CO2非混相驱和周期注气4 种驱替方式,研究不同渗透率级别岩心的驱油效率和剩余油分布,以此对大庆现场注CO2先导实验区开发提供参考意见。结果表明,在相同条件下,常规注水开发的效果最差,但转注气后能有较大的提升;对于特低渗岩心,周期注气的驱油效率最高;对于超低渗岩心,注水转注气的效果高于其他3 种方式。剩余油分布研究表明,注水转注气、CO2混相驱和CO2非混相驱3 种方式动用的主要是大-中孔隙中的油,对于黏土微孔隙中的原油很难进行动用,但是通过周期注气过程中的停注时间,在毛管力和弹性能的作用下,微孔隙中的原油向中-大孔隙中流动,从而增加小孔隙中难动用的原油的动用程度。
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.
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