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

Abstract

CO2 sequestration in shale is of great potential and has the feasibility to achieve dual purposes: CO2 emission reduction and CH4 production enhancement. Nevertheless, challenges still remain in working out an obliged strategy prior to the industrial CO2 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 CO2 injection well (IW) and the CH4 production well (PW) on the CO2 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 CO2 sequestration and simultaneous CH4 recovery. A longer IW–PW distance is beneficial for CO2 storage, while a shorter one is conducive to recovering CH4 from the depleted WL shales. For any set of the IW–PW combos, vertical heterogeneity universally goes to the performance of CO2 sequestration, CH4 recovery, and EGR efficiency. For optimization, the injection of CO2 from the bottom reservoir, accompanying a longer IW–PW horizontal distance, is a better choice for geological CO2 storage in depleted WL shales. Using a customized CS-EGR efficiency (ECS-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 CO2 in the depleted WL shales while enhancing shale gas recovery.

Topics & Concepts