Preliminary Investigation of the Hydraulic Stimulation for a Field-Scale Forge Candidate Geothermal Reservoir

In order to develop, test, and improve technologies and techniques for the creation of sustainable EGS (Enhanced Geothermal Systems), FORGE (Frontier Observatory for Research in Geothermal Energy) project has been led by U.S. Department of Energy. Since the abundant datasets for both geology and geophysics of the Fallon FORGE site are available, we can prepare the conceptual 3-D geologic model by integrating them. In this study, we report the preliminary results of numerical simulation on the hydraulic stimulation response at this candidate site. We first design the discrete fracture network for the region of 1200×800×800 m volume, which includes approximately 2000 fractures. Then we explore the responses during hydraulic stimulation via the "SHIFT" based simulator (i.e., AI-SHIFT2). A series of stimulations are performed in six stages/zones along the horizontal well and both low (5 kg/s) and high (80 kg/s) injection rates are specified in order. In our simulations, the ratio of stimulated (slipped / sheared) fractures volume to total volume of pre-existing fractures are evaluated to be 1~2%. On the other hands, this ratio has been evaluated to be 10~20% by U.S. group, who adopt DEM (distinct element method) based simulator. Such a large discrepancy may be attributed to whether the propagation of newly created fractures is adequately taken into consideration or not.