Seepage and Heat Transfer Characteristics of CO2 Plume Geothermal Systems Under Different Injection Conditions

CO2 plume geothermal systems (CPGS) hold significant potential for geothermal energy extraction due to their dual benefits of carbon sequestration and efficient heat transfer. Existing studies primarily focus on macroscopic models of geothermal systems, with limited evaluation of real thermal reservoir cores in terms of CPGS heat extraction performance. This study investigates the seepage and heat transfer characteristics of CO2 under various injection conditions through a combination of experiments and numerical simulations. Experimental results indicate that under the tested conditions, CO2 exhibits 20–50% higher heat transfer capacity compared to distilled water. The heat transfer capacity increases with injection flow rate, while injection temperature shows a relatively limited influence under high-velocity seepage conditions. Specifically, at low injection flow rates, lower injection temperatures result in higher heat transfer capacity due to the increased thermal driving force between CO2 and the reservoir rock. Microscale seepage-heat transfer simulations reveal that an increase in injection flow rate enhances CO2 flow velocity within the pore network, expands the swept volume, and consequently strengthens convective heat transfer and increases the effective heat exchange area. Additionally, higher thermal reservoir temperatures establish a greater temperature gradient between the working fluid and rock, thereby enhancing heat transfer between CO2 and the reservoir rock. The findings of this study provide valuable insights for optimizing CPGS design, particularly in understanding the impact of injection conditions on heat transfer capacity, with both practical engineering and theoretical implications.