Multi-physics coupling mechanisms and key development factors in enhanced geothermal systems for hot dry rock

Hot dry rock (HDR) geothermal energy is a clean, renewable resource whose efficient development is essential for advancing energy transition and achieving green, low-carbon objectives. Enhanced geothermal systems (EGS), which extract heat by hydraulically connecting injection and production wells, have emerged as the primary technological approach for HDR exploitation. This study systematically investigates the development mechanisms and key influencing factors of EGS using H2O as the working fluid, through integrated theoretical modeling and numerical simulation. By introducing a dynamic matrix porosity–permeability model to modify the governing equations, a multi-physics coupled model better aligned with practical EGS development is established. Based on this, a discrete-fracture numerical model is developed to analyze the impacts of well configuration, development parameters, and fracture network structure on thermal performance. Results show that, driven by pressure gradients and gravity, a vertically aligned single-injection single-production horizontal well achieves superior heat extraction, with cumulative heat production 5 % higher than other configurations under an injection rate of 1000 m3/d. Sensitivity analysis shows that increased matrix porosity and permeability reduce heat recovery due to fluid entrapment and flow diversion, whereas for engineering parameters, injection temperature has limited impact on thermal performance, while the injection–production pressure differential significantly enhances system efficiency. Further analysis shows that a uniformly distributed fracture network improves thermal performance, and that moderately increasing fracture aperture further enhances heat extraction capacity, while secondary fractures enhance fluid recovery but contribute little to total heat extraction. This study deepens the understanding of multi-physics coupling in EGS and offers theoretical and technical support for optimizing development and achieving carbon peaking and neutrality goals.