Lawrence Berkeley National Laboratory

In order to understand the details of thermal and hydrologic processes attending CO2 injection into a deep aquifer in the context of Carbon Capture and Storage (CCS), we have carried out coupled well-reservoir simulations of CO2 injection using the simulator T2WELL-ECO2M. We focus on the injection of cold, dry CO2 into a warm aquifer and analyze in detail the thermal and hydraulic processes of the coupled well-reservoir system. The results demonstrate the effectiveness of T2WELL in accurately modeling non-isothermal, multiphase flow, phase changes, and identifying dry-out regions in porous media. We simulated heat exchange with the ambient environment, friction effects, convection, exothermic dissolution in brine, and cooling due to both Joule-Thomson effect and water vaporization. The temperature profile within the wellbore deviated from the geothermal profile, impacting CO2 properties at the bottomhole. The simulation revealed the presence of three fronts in the formation: the CO2 saturation, thermal, and evaporation fronts. The thermal and evaporation fronts were located farther behind the saturation front, indicating limited dry-out and thermal effects near the wellbore. This simulation capability and insights gained in this study form a foundation for ongoing work such as sensitivity analyses, injection optimization, performance assessment, and operational decision support.