Low permeability geothermal reservoirs can be stimulated by hydraulic fracturing to create Enhanced (or Engineered) Geothermal Systems (EGS) with higher permeability and improved heat transfer to increase heat production. In this paper, we document our effort to develop a numerical simulator with explicit geomechanics-discrete flow network coupling by utilizing and further advancing the simulation capabilities of the Livermore Distinct Element Code (LDEC). The important modules of the simulator include an explicit finite element solid solver, a finite volume method flow solver, a joint model using the combined FEM-DEM capability of LDEC, and an adaptive remeshing module. The numerical implementation is verified against the classical KGD model. The interaction between two fractures with simple geometry and the stimulation of a relatively complex existing fracture network under different in-situ stress conditions are studied with the simulator.