Strategy Optimization on Industrial CO2 Sequestration in the Depleted Wufeng-Longmaxi Formation Shale in the Northeastern Sichuan Basin, SW China: From the Perspective of Environment and Energy

CO 2 sequestration in shale is of great potential and has the feasibility to achieve dual purposes: CO 2 emission reduction and CH 4 production enhancement. Nevertheless, challenges still remain in working out an obliged strategy prior to the industrial CO 2 sequestration operation in a real shale formation that inevitably contains a strong heterogeneity in reservoir parameters. This study attempts to simulate the complex anisotropic condition of depleted Wufeng-Longmaxi (WL, for short) formation shales (NE Sichuan basin) using a multifield coupled model, in a quantitative manner, focusing on the interference from the relative locations of the CO 2 injection well (IW) and the CH 4 production well (PW) on the CO 2 sequestration and enhanced gas recovery (CS-EGR). According to the novel modeling, numerical results indicate the CS-EGR output from each one of nine preset IW–PW combos differs. The IW arranged at the bottom WL shales is better for CO 2 sequestration and simultaneous CH 4 recovery. A longer IW–PW distance is beneficial for CO 2 storage, while a shorter one is conducive to recovering CH 4 from the depleted WL shales. For any set of the IW–PW combos, vertical heterogeneity universally goes to the performance of CO 2 sequestration, CH 4 recovery, and EGR efficiency. For optimization, the injection of CO 2 from the bottom reservoir, accompanying a longer IW–PW horizontal distance, is a better choice for geological CO 2 storage in depleted WL shales. Using a customized CS-EGR efficiency ( E CS-EGR ), C3–150 is treated as the recommended strategy in this work. Generally, the simulation results are expected to be implicative for the confirmation of the optimized IW–PW pattern that serves for the sequestration of CO 2 in the depleted WL shales while enhancing shale gas recovery.