低渗透油藏 CO2驱油效果评价

摘要

Low permeability reservoir with water flooding has some features such as low recovery rate and difficult water injection. In this paper, the specific reservoir geology, crude oil physical properties and the minimum miscible pressure conditions were analyzed. It's determined that the reservoir can meet requirements of CO2 miscible displacement. Numerical simulation software Eclipse was used to simulate the reservoir. Three development ways of continuous water injection, continuous gas injection and cycle gas injection were compared, it's found that the cycle gas injection has the best effect. When the ratio of injection time to stop time is 2:1, the degree of reserve recovery is the highest, the reason is that the energy propagation of the low permeability reservoir makes the formation pressure distribution more uniform when the time ratio is 2:1. By comparing different CO2 displacement pressure, it's found that when the displacement pressure is equal to CO2 minimum miscible pressure, the degree of reserve recovery is the highest. When displacement pressure is greater than the minimum miscible pressure, with the increase of pressure, the lower the degree of reserve recovery, the reason is that the reservoir has been blocked.%针对低渗透油藏水驱采收率低，注水困难的特征，通过分析具体油藏的地质、储层及原油物性和最小混相压力等条件，确定了该油藏满足迚行 CO2混相驱的要求。使用数值模拟软件 Eclipse 对该油藏迚行模拟，对比连续注水、连续注气和周期注气三种开发方式，发现周期注气开发效果最好。当注停时间比为2：1时采出程度最高，分析其原因为注停时间比为2：1时，低渗透油藏能量的传播使地层压力重新均匀分布。对比不同 CO2驱替压力，发现当驱替压力在 CO2最小混相压力附近时采出程度最高，驱替压力大于最小混相压力，随着压力增大，采出程度越低，分析原因为储层发生堵塞现象。