Numerical investigation of flow distribution and energy extraction in multi-fractured doublet Enhanced Geothermal Systems (EGS)

Enhanced Geothermal Systems (EGS) offer significant potential for sustainable, high-temperature energy extraction, yet their efficiency depends strongly on how fluid flow and heat transfer evolve within complex fracture networks. This study introduces a novel numerical framework that captures the coupled flow and thermal behavior in a multi-fractured EGS by solving the Forchheimer and energy equations simultaneously within both wells and fractures using the finite element method. Four EGS configurations—parallel, anti-parallel, converging, and inclined—are evaluated to examine the influence of fracture permeability, porosity, inlet velocity, inlet temperature, and well inclination on fluid distribution and thermal performance. Results demonstrate that the anti-parallel configuration provides the most balanced flow distribution, minimal short-circuiting, and the highest production temperatures, while the converging configuration exhibits the weakest thermal performance due to accelerated flow convergence and reduced residence time. Permeability strongly governs velocity redistribution and thermal sweeping, whereas porosity plays only a secondary role. Increasing inlet velocity decreases fracture temperatures by shortening residence time, whereas higher inlet temperatures produce nearly proportional increases in production temperature. Well inclination modifies flow alignment and thermal gradients, with moderate angles offering optimal heat extraction. This study emphasizes the crucial importance of coordinating fracture geometry, flow resistance, and operational parameters to optimize thermal recovery in EGS reservoirs. Water produces higher but more uneven velocities across the fractures, whereas supercritical CO 2 maintains a more uniform flow with a comparable downstream velocity increase, indicating its suitability for stable heat extraction in antiparallel EGS systems. These findings provide a basis for optimizing fracture-network design and motivate future studies on advanced working fluids, such as nanofluids and water–CO 2 mixtures, which offer tunable thermophysical properties and the potential to balance heat transfer enhancement with flow uniformity for improved geothermal energy extraction efficiency.