库车北部构造带低渗透油藏油水互驱变化规律及机理

Variation Law and Mechanism of Oil-Water Mutual Drive of Low Permeability Reservoir in Northern Kuqa Structural Belt

对库车北部构造带不同渗透率的岩心进行正反向水驱油试验,采用CT扫描技术、最大球法和微观孔隙模型的孔隙特征统计方法进行三维重构,获取岩心内束溥水状态、正向驱至残余油状态和反向驱至残余油状态,进而总结机理及规律。结果表明:当岩心含水率为100%时,其总驱油效率与渗透率拟合所得关系系数为0.7190,低于正驱驱油效率与渗透率的拟合系数0.8199,表明岩心渗透率并非反驱过程中残余油增量的主控因素;转抽时含水率越低的岩心,转抽驱油效率增量越高;在不同含水率条件下驱油效率随渗透率变化呈现一定的规律性变化,当含水率达到100%时,驱油效率增量随渗透率的变化基本保持不变;不同驱替状态下岩心孔隙半径和喉道半径变化与驱替过程中岩心孔隙内束缚水、残余油的运动状态有关;反向驱油可以实现残余分散油的重新聚集,从而提高采收率。

The forward and reverse water displacement tests were carried out on cores with different permeability in northern Kuqa structural belt,and the three-dimensional reconstruction was carried out by using CT scanning technology,the maximum sphere method and pore characteristic statistical method of the micro-pore model to obtain the state of irreducible water in the core,the state of forward displacement to residual oil,and the state of reverse displacement to residual oil,and then to summarize the mechanism and laws.The results showed that when the core water content was 100%,the fitting coefficient between total displacement efficiency and permeability was 0.7190,which was lower than fitting coefficient between forward displacement efficiency and permeability of 0.8199,indicating that core permeability was not the main controlling factor of residual oil increment in the process of reverse displacement.The core with lower water content could obtain higher oil displacement efficiency increment.Under the condition of different water content,the oil displacement efficiency showed a regular change with the change of permeability.When the water content reached 100%,the oil displacement efficiency increment remained basically unchanged with the change of permeability.The changes of pore radius and throat radius in different displacement conditions were related to the movement state of bound water and residual oil in core pores during displacement.Reverse flooding could achieve re-aggregation of residual dispersed oil for enhanced oil recovery.