Numerical simulation of hydraulic fracture propagation in hot dry rock reservoirs integrating wellbore-reservoir-fracture

Hot dry rock (HDR) represents a typical high-temperature, ultra -low permeability reservoir, where hydraulic fractures must be created to provide efficient heat-exchange pathways for geothermal energy extraction. In this paper, a fully thermal-hydro-mechanical (THM) coupled numerical model for HDR reservoirs' hydraulic fracturing was established to study the hydraulic fracture propagation mechanism and reservoir mechanical response characteristics under low-temperature shock. The half-fracture length calculated by the KGD model was compared with the simulation results to verify the model's accuracy. The results show that the tensile stress and temperature gradient at the low-temperature shock boundary are relatively high. After the rock fractures, the temperature and tensile stress values inside the rock decrease but their range expands. The hydraulic fracture morphology is more sensitive to reservoir temperature than to the thermal expansion coefficient. Furthermore, the temperature hysteresis effect produced by the increase in injection displacement reduces the thermal stress at the fracture tip. [Received: September 6, 2024; Accepted: August 11, 2025]