CO 2 storage with enhanced gas recovery (CSEGR) in a depleted gas reservoir was a promising strategy for mitigating CO 2 emission and enhancing gas recovery. A reservoir model incorporating four reservoir gases was built based on the geological determination of the offshore Ya 13-1 gas field in the Qiongdongnan Basin, South China Sea. The model adopted a four-stage framework and two configurations to evaluate the strategy of CSEGR by TOUGH + RealGasBrine. The four stages were CO 2 preinjection (I), simultaneous injection and production (II), continuous injection (III), and monitoring (IV). The five-well configuration was developed to assess the injection duration of Stage I and the perforation length of the production well. The six-well configuration evaluated further the injection rate of Stages I and II. Results showed that a 5-year preinjection could balance the project duration, mass flow rate, and the final recovery of hydrocarbon gas, and full perforation maximized the recovery. The final recovery factor of CH 4 + C 2 H 6 increased from 50.8% to 64.7% at the end of Stage II while varying the injection rate. The reservoir pressure was set to the untapped one by the end of Stage III. The theoretical storage of CO 2 was 310 Mt via the above strategy, 5.5% of which dissolved over the 200-year monitoring period (Stage IV). The integrated profit from incremental gas production and carbon sequestration was 135.5 to 290.8 billion USD. The framework and quantitative insight here provided guidance for the preliminary planning of the CSEGR project in the Ya 13-1 gas field and may serve as a reference for future studies on similar depleted offshore gas reservoirs worldwide.
F et al. (Sun,) studied this question.