Abstract: Systems and methods for simulating subterranean regions having multi-scale, complex fracture geometries in a realistic simulation environment, which includes in the modeling process three-dimensional multi-scale rock discontinuities, hydraulic fractures, and heterogenous reservoir properties. Non-intrusive embedded discrete fracture modeling formulations are applied in conjunction with commercial or in-house simulators to efficiently and accurately model subsurface characteristics including three-dimensional geometries having combinations of complex hydraulic fractures and multi-scale rock discontinuities.