Numerical Research of Thermo–Hydro–Mechanical Response and Heat Transfer in a Multiwell EGS with Rough-Walled Fractures after Shear Deformation

Abstract

Natural fractures may not be developed in hot dry rock reservoirs, and tectonism or fracturing can induce the shear deformation of fractures and result in large-scale rough-walled fractures. Previous studies usually ignore the effect of rough walls on production performance. This study constructs a 3D multiwell enhanced geothermal system (EGS) model with two rough-walled fractures after shear deformation, systematically investigates the response characteristics of each physical field under the thermo–hydro–mechanical coupling, and determines the effect of the distribution of two rough-walled fractures and the relationship between the well layout scheme and the shear deformation direction on the production performance. The obtained results indicate that the distribution and evolution of the temperature and seepage fields are controlled by the fractures. The stress has a clear impact on the fracture permeability, up to approximately four times the initial permeability. The water preferentially extracts the heat from the reservoir rock between fractures. When the intersecting angles of fractures are 10° and 30°, there exists a sufficient heat exchange domain and a shorter average distance between fractures, which can enhance the production efficiency. The well layout perpendicular to the shear deformation direction is conducive to delaying the lifespan of the EGS and extracting more heat over a longer exploitation time. These key results can provide reasonable suggestions for the optimal development strategy in EGSs.