Physics-based modeling of fracturing and permeability evolution in engineered geothermal reservoir

In order to further understand strongly coupled flow and fracturing processes during hydraulic simulation of engineered geothermal system (EGS) reservoir, we developed a physics-based rock deformation and fracture propagation model by using a discrete element model (DEM) to explicitly describe fracture initiation and propagation induced by fluid injection, and a network flow model to simulate fluid flow in both fractures and porous rock matrix. The fluid pressure gradient exerts forces on individual solid elements of the discrete element network, which then deforms the mechanical bonds and breaks them if the deformation reaches a prescribed threshold value, thereby initiating fracturing, which in turn changes the permeability of flow network. Simulation results for fracture generation and growth patterns due to fluid injection under various confinement conditions will be presented and discussed.