Co-optimization of oil recovery and CO2 storage for cyclic CO2 flooding in ultralow permeability reservoirs

Cyclic CO 2 flooding is an efficient method to enhance oil recovery in ultralow permeability reservoirs. As the demand for low carbon economy development, co-optimization of CO 2 storage and utilization should be considered. In this research, initially a comprehensive optimization method was proposed, which co-optimize oil recovery and CO 2 storage by different weighting factors. Then, a series of core flooding experiments were performed using the core samples collected from Changqing oilfield, which is a ultralow permeability reservoir with heterogeneity and micro-cracks, CO 2 injection parameters of slug size and Injection-Soaking Time Ratio (ISR) were optimized. The results revealed that the optimal injection parameters changed for different optimization objectives. In the case where equal important to oil recovery and CO 2 storage were considered, the optimum CO 2 injection parameters in the ultralow permeability reservoirs were 0.03PV for slug size and 1:1 for ISR. Comparing the method of oil recovery optimization ( ω 1  = 1) to co-optimization of oil recovery and CO 2 storage ( ω 1  =  ω 2  = 0.5), oil recovery was reduced by 8.93%, CO 2 storage was significantly increased by 25.85%. The results provide an insight into parameter optimization of CO 2 enhanced oil recovery design.