Geomechanical Analysis of EGS Reservoir Development in Normal, Strike-Slip and Thrust Faulting Terrains

Abstract

Stimulation by hydro-shearing and hydraulic fracturing changes the intensity of significant conducting fractures and their transmissivities in EGS reservoirs. These changes lead to a variety of preferential flow path geometries which affect the thermal and impedance performance of the reservoir. Starting with geologically realistic discrete fracture network (DFN) models in differing regional stress states, this paper examines the evolution of block size measures during lower pressure, longer duration hydro-shearing stimulation and the resulting stimulated fractures apertures and transmissivities. Block size and shape are shown to significantly influence reservoir thermal depletion. As stimulation pumping-pressure increases, the significant fractures for thermal production align with the minimum stress direction while flow is preferentially channeled in the maximum horizontal stress direction. In normal and strike-slip stress regions, fractures may open preferentially at shallower depths due to larger differentials between the pumping pressure and the in situ stresses, thus driving flow-path creation towards shallower, cooler rock.