CO2 injection for heat extraction and carbon sequestration in a geothermal site: Huizhou Sag, the Pearl River Mouth Basin

Recently more attention has been paid to CO2 geological storage combined with geothermal water recovery (CO2-EWR). In this regard, the production performance of a geothermal site in Huizhou Sag was evaluated. In the process of evaluation, a new technology in which cold water is injected through the tubing and CO2 through the annulus is used and simulated. In this study, a conceptual model was established by coupling the wellbore and the geothermal reservoir according to the field exploration data. The power production performance was evaluated by using the output from the wellbore-reservoir coupled simulation. The numerical simulation outputs showed a temperature difference of approximately 5.5 °C from well bottom to wellhead at the beginning. The 3D-visualization of CO2 distribution demonstrates two steps of migration, vertical migration and horizontal spreading. It was also found that injecting water above CO2 plays a significant role in preventing rising of CO2 “bubble” in the early stages of injection process. The results of thermodynamic simulations suggests the desired thermal production efficiency and gross power output could be obtained. In addition, the impact of various parameters on simulation results were investigated and analyzed, the analysis results provided a better understanding of CO2-EWR (CO2 geological storage enhanced with geothermal resources recovery) technology as well as practical perforation depth of the wells.