Indoor experimental study on injection-production heat transfer of enhanced geothermal system

ABSTRACT: The fluid flow and heat transfer characteristics in fracture systems are crucial to efficient geothermal energy development, directly influencing heat transfer medium leakage and long-term heat extraction efficacy. However, numerical simulations based on idealized assumptions and single-fracture flow heat transfer experiments with small rock samples struggle to accurately replicate the actual injection-production heat transfer process in hot dry rock (HDR) systems. Currently, there remains a gap in experimental research on large-scale injection-production heat transfer processes in HDR systems. This study utilizes a self-developed true triaxial injection-production physical simulation experiment system to conduct heat transfer experiments under various injection-production modes. The heat transfer process was analyzed by collecting parameters such as flow rate, temperature, and production pressure difference during the experiment, examining the conversion mechanism between heat exchange and leakage channels. Results indicate that an increase in the number of production wells enhances heat extraction efficiency but also exacerbates seepage competition and fluid loss between fractures. Further analysis reveals that heat transfer performance is constrained by two key factors: the presence of dominant channels, which limit the heat transfer area's full utilization, and fluid leakage, which directly impacts production flow. This study offers novel experimental insights supporting the long-term and efficient development of HDR geothermal resources.