Numerical Simulations of Hydraulic Fracturing in Carbonate‐Type Hot Dry Rock Reservoirs Based on the Coupled Thermo‐Hydraulic‐Mechanical‐Damage (THMD) Model

ABSTRACT Hydraulic fracturing technology is widely used in Enhanced Geothermal System (EGS) projects to induce fractures and enhance the permeability of thermal reservoirs. The hydraulic fracturing process of hot dry rock (HDR) is actually a multiphysics coupling process that couples the heat transfer field, seepage field, stress field, and damage. This study selected carbonate‐type HDR as a research object to test its basic mechanical parameters. Then, a Thermal‐Hydraulic‐Mechanical‐Damage (THMD) coupling model of the HDR hydraulic fracturing process based on elastic thermodynamics was developed. The model accuracy was also confirmed through experimental verification. This study investigated the impact of different in‐situ stress conditions, temperature conditions, and injection parameters on the initiation and propagation of hydraulic fractures in HDR. Simulation results indicate that under high‐temperature conditions, the breakdown pressure decreases and propagates, widening the existing fracture under the same condition. The variation in stress difference will reduce the microfractures, and an increase in confining stress restricts the extension of fractures and increases the breakdown pressure of the rock. The results of this study can be compared with actual EGS projects, providing guidance for parameter designs and improving EGS development efficiency.