Enhancing reservoir stimulation and heat extraction performance for fractured geothermal reservoirs: Utilization of novel multilateral wells

Enhanced Geothermal System (EGS) is a promising approach to improve the production efficiency of deep geothermal energy (e.g. hot dry rock). However, it faces with significant unsolved challenges to create connected fracture networks between injection-production wells, maintain high flow rates and obtain sufficient thermal power in EGSs. To address these challenges, we propose a novel multilateral-well EGS method for improving the performance of both reservoir stimulation and heat extraction from hot dry rock. In this contribution, we construct an integrated numerical model to simulate the processes of complex fracture propagation and thermal heat production as a whole. This model fully couples fluid flow, heat transfer, rock deformation and fracture propagation, taking into account the generation of new fractures, reactivation of pre-existing fractures, and mechanical interaction between hydraulic and natural fractures. The reliability of the integrated model is well verified with the analytical solution and experimental data. Subsequently, the damage and temperature fields as well as the resulting heat extraction performance of the multilateral-well EGS and conventional vertical-well EGS are compared. The results indicate that the stimulated reservoir permeability and connectivity, extracted thermal power under the configuration of multilateral-well EGS are much higher (about an order of magnitude) than those under the scheme of vertical-well EGS. This study presents a promising alternative for EGS to achieve enhanced reservoir stimulation and heat extraction performance.