Wellbore-reservoir and multiphysics coupling model for liquid CO2 cyclic injection in a CCUS-EGR framework

Natural gas is a vital underground clean energy resource and inject CO₂ into gas reservoirs can enhance natural gas production while simultaneously reducing carbon emissions. In this study, we developed an extended wellbore-reservoir-thermo-hydro-mechanical-diffusion (WR-THMD) coupling model to establish a comprehensive closed-loop framework for carbon capture, utilization, and storage-enhanced gas recovery (CCUS-EGR). Utilizing this model, we investigated the operational conditions of the wellbore and reservoir, focusing on the effects of engineering parameters on system performance. The results indicate that to optimize system CO₂ storage capacity, stabilize the pressure differential between the wells, and enhance storage efficiency, we recommend employing relatively low injection mass flow rates and injection temperatures. When designing wellbore parameters, it is crucial to account for significant temperature losses in the production well, as these losses substantially raise the flow obstruction of the produced gas and direct to potential thermal energy loss. Lower injection mass flow rates can effectively minimize thermal losses and delay CO₂ breakthrough in the production well. This study provides a foundational framework for effectively managing CCUS-EGR systems, aiding in the advancement of underground clean energy production and CO₂ storage.