Spatiotemporal Variations in Fluid and Sand Temperature Fields During Sc-CO2 Fracturing

Supercritical carbon dioxide ($\text{Sc}-\text{CO}_2$) fracturing can create complex fracture networks, thereby effectively enhancing production capacity. Additionally, it has the potential to sequester $\mathbf{{CO}_{2}}$ underground, reducing net $\mathbf{{CO}_{2}}$ emissions, making it a promising fracturing method. However, the density of $\mathbf{{Sc}}-\mathbf{{CO}_{2}}$ varies significantly with temperature, which greatly affects the transport of sand and, consequently, the placement of sand within the fractures. To systematically analyze the heat transfer mechanisms during the sand transport process in supercritical $\text{CO}_2$ and its impact on the temperature fields of the sand bed and supercritical $\mathbf{{CO}_{2},}$ this study integrates a heat transfer model into the Computational Fluid Dynamics-Discrete Element Method (CFD-DEM) model. The research findings indicate that, due to the complex heat transfer mechanisms among sand particles, $\mathbf{{Sc}-\text{CO}_{2}}$ fluid, and the fracture walls, the $\mathbf{{Sc}-\text{CO}_{2}}$ and sand bed temperature fields exhibit significant spatiotemporal changes. The sand bed temperature increases with increased sand thermal conductivity, decreased injected velocity, and enhanced fracture wall temperature. However, the efficiency of heat transfer is influenced differently by various parameters. The temperature in the fluid region is affected by the fluid-sand and fluid-wall heat transfer efficiencies, as well as the shape of the sand bed. These results provide data support and a theoretical foundation for the design of supercritical $\mathbf{{CO}_{2}}$ fracturing.