Numerical evaluation of CO2-based enhanced oil recovery approach applied in a heterogeneous tight oil reservoir: Gas channelling alleviation and parameters optimization

In this study, a numerical simulation approach was employed to conduct CO2 continuous gas injection (CCGI) and CO2-WAG processes in a heterogeneous tight oil reservoir. Firstly, operation parameters of CCGI technique, including injection pressure, injection rate, production-injection pressure difference, and well pattern, were optimized. The CO2 movement in low and high permeability zones, light component extraction, and gas channelling were investigated. Then, both schemes were assessed under identical base conditions to investigate the impact of WAG on gas channelling and mitigate its negative influence. Lastly, CO2-WAG process is optimized by identifying the optimal WAG ratio, production pressure, and wells distribution, followed by a comparative evaluation of all cases. The results indicate that CCGI achieves the best production performance with injection pressure of 30 MPa, injection rate of 50000 m3/day, production pressure of 6 MPa, and well pattern of regular five spot. CO2-WAG process significantly alleviates channelling, resulting in 3.84 % oil recovery factor (ORF) increment, and the production performance gets optimized under WAG ratio of 1:2 and production bottom hole pressure of 2 MPa. The integrated optimization of CO2-WAG-regular seven spot coupled with infill well accomplished the highest ORF of 49.69 % among the researched scenarios. This work supplies a deeper knowledge of gas channelling and parameters optimization in the CO2-EOR process in the tight reservoirs, and can be a guideline to carry out a prospective pilot test in the targeted reservoir in the future.