<p>Enhanced geothermal system (EGS), typically designed as a doublet of injection and production wells, is a promising approach to exploit hot dry rock (HDR) resources. However, modeling fluid flow and heat transfer in fractured reservoirs remains challenging due to multi-scale fracture heterogeneities and coupled interactions. This study develops a three-dimensional discrete fracture network (DFN)-based thermal-hydraulic coupling model solved by the finite element method (FEM) to efficiently evaluate the heat extraction performance of fractured HDR reservoirs. The developed modeling scheme is validated against analytical and numerical benchmarks, and then applied to a large-scale fractured geothermal reservoir. Results show that the heterogeneity of the fracture network leads to a highly uneven temperature distribution, with the cold front advancing along the primary percolating fracture network pathways. Higher injection temperature and larger fracture aperture accelerate the geothermal reservoir cooling, while the increased well spacing extends EGS lifetime and reduce the electricity cost. This research provides deeper insights into the development of 3D EGS and supports the optimization of operational parameters and economic feasibility.</p>