Performance evaluation of CO^sub 2^ flooding process in tight oil reservoir via experimental and numerical simulation studies

In this study, experimental and numerical simulation studies were conducted to enhance oil production in a tight oil reservoir using CO2 injection processes. In experimental studies, three types of CO2 injection experiments-CO2 flooding (continuous CO2 injection process), CO2 flooding coupled with a soaking period, and CO2 flooding coupled with pressure maintenance-were carried out in one-meter-long core plugs to investigate the effect of CO2 flooding schemes on production performance. The properties of light oil–CO2 systems with different CO2 concentrations under different pressures were measured to study the phase behaviors of light oil–CO2 systems. Test results indicate that the CO2 flooding process is the best method to enhance oil recovery in tight formations, showing an oil recovery factor of 38.96% and a CO2 utilization of 10.41 Mscf/STB. In numerical simulation study, the properties of light oil–CO2 systems first were simulated using the WinProp module. Next, the GEM module was applied to implement history-matching studies on experimental results, and good agreement was achieved. Third, a sensitivity analysis was carried out to investigate the effect of parameters on the CO2 flooding process. Finally, upscaling simulation studies were conducted at the field scale to optimize the well pattern and CO2 injection rate to enhance oil recovery in the target reservoir. Important correlations on the effect parameters were generated for predicting the oil production performance in the reservoir with different operations. Among the studied well patterns, the inverted seven-spot well pattern with a CO2 injection rate of 44.28 t/day/well achieved the best production performance in the field study. In the optimized case, the oil recovery factor reached 30.89% with a low CO2 utilization of 5.69 Mscf/STB.