Enhanced geothermal systems with horizontal wells in anisotropic layered reservoirs: Sensitivity analysis and performance evaluation of heat recovery

Horizontal wells in enhanced geothermal systems (EGS) enhance heat extraction efficiency compared to vertical wells, owing to extended contact with fractured reservoirs. However, the heterogeneous and anisotropic nature of layered rock formations challenges conventional isotropic models. This study proposes a novel 3D heterogeneous and anisotropic layered reservoir model for horizontal well EGS, specifically addressing the oversimplification of prior studies. The strategic placement of injection and production wells across layered formations significantly controls fluid percolation patterns, governed by the fracture networks and the anisotropy of rock permeability. The best-performing configuration (injection in Layer 2, production in Layer 4) achieves a maximum effective power of 10.79 MW higher than conventional vertical well systems under similar conditions-with a flow impedance of 0.1227 MPa/(kg·s) and heat recovery ratio of 36.67%. Sensitivity analyses reveal that power generation is dominantly influenced by the injection flow rate. This is attributed to its direct impact on convective heat transfer. In contrast, fracture spacing (25-75m) shows limited sensitivity, which is due to scale-dependent homogenization. The preferred parameters (50 m fracture spacing, 333 K injection temperature, 0.15 m³/s flow rate) align with commercial viability criteria. This strategy reduces drilling costs by prioritizing high-permeability layers for injection. This study provides a validated framework for parametric evaluation and screening of EGS design in complex geothermal reservoirs.