Numerical Simulation of Enhanced Geothermal Systems Using a DPDK+EDFM Hybrid Fracture Model

Existing numerical simulation methods for enhanced geothermal systems (EGS) in hot dry rock fail to adequately account for the multiscale media (including matrix rock, natural fractures, and large-scale fractures) within stimulated reservoir volumes. This deficiency results in unreasonable predictions of both temperature distribution and EGS production performance. This study proposes a hybrid fracture model that integrates the dual-porosity–dual-permeability (DPDK) model with the embedded discrete fracture model (EDFM). Building upon this framework, the corresponding thermal–hydraulic simulation method is developed to simulate the heat extraction processes in EGS. Numerical simulation results demonstrate that the hybrid fracture model effectively captures the temperature distribution across multiscale media. It confirms that fractures act as the dominant channel for heat extraction, while identifying the matrix as the primary heat storage zone. Sensitivity analysis reveals that the heat extraction performance improves with decreased natural fracture spacing, increased natural fracture permeability, and reduced large-scale fracture permeability. In contrast, matrix permeability shows a minimal influence on the heat extraction performance. This study advances the numerical simulation method for EGS and elucidates the effects of multiscale media on the heat extraction performance of EGS.