Experimental study on convective heat transfer of scCO2 with a middle-high permeability pore scale cretaceous sandstone

In the context of the two - carbon goal, the large - scale utilization of carbon dioxide medium, especially in geothermal resource development, is crucial for reducing non - renewable resource consumption and promoting a green - low - carbon future. The heat generated can be applied in power generation, energy storage, heating, etc., enhancing energy efficiency. Research on convective heat transfer between supercritical carbon dioxide (scCO₂) and porous medium rocks is gaining importance for its applications in geothermal energy and carbon capture. Based on middle - deep geothermal research, a flow - heat - transfer test bed for high - temperature and high - pressure supercritical fluids and porous media was constructed. Different injection flow rates were experimentally compared and analyzed. Results show that the convective heat transfer is complex, related to fluid and rock properties, flow rate, and temperature gradient. Under reservoir-related conditions, combining pore-scale CT analysis with high-temperature and high-pressure experiments, it is found that the cemented structure of Cretaceous sandstone increases the convection efficiency of scCO₂ by 20–35 %. Nusselt number curves were fitted, and local convective heat transfer on the fracture surface was analyzed. Higher flow rates lead to better heat recovery per unit mass flow rate and faster production temperature drops. Rock initial temperature impacts fluid exit temperature and heat transfer. Novel insights into scCO₂ tortuous flow dynamics and calcite-cemented microstructure interactions are provided, advancing geothermal reservoir simulation accuracy.