Quantitative analysis of fracture network geometry on fluid flow and heat transfer in hot dry rock geothermal reservoirs

Hot dry rock geothermal energy relies on optimized fracture networks for efficient thermal energy extraction. This research employs the finite element method to establish a discrete fracture network (DFN) model that integrates fluid mechanics and thermodynamics within a porous medium, enabling a comprehensive assessment of the coupled impact of varying fracture lengths and densities on production performance. Unlike prior studies focusing on uniform or simple fracture networks, our model simulates fluid flow and heat transfer under complex fracture configurations, offering a quantitative framework to evaluate key physical properties such as fluid pressure, Darcy velocity, and temperature. Results reveal that networks with moderate fracture lengths and densities form effective flow channels, maintain pressure gradients and Darcy velocity between wells, and improve overall flow and thermal extraction efficiencies, thereby extending the lifespan of geothermal projects. Conversely, low fracture density or excessive unconnected short fractures hinder fluid movement and heat exchange, while overly long fractures lead to rapid pressure drops and temperature declines, posing sustainability challenges. Optimizing fracture length and density is essential to sustaining extraction efficiency and preventing rapid thermal dissipation. These insights lay groundwork for theoretical optimization of fracture networks and are critical for designing efficient, durable hot dry rock energy systems.