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

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 0.719 0, which was lower than fitting coefficient between forward displacement efficiency and permeability of 0.819 9, 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.