PROCEEDINGS, The 8th Indonesia International Geothermal Convention and Exhibition (IIGCE) 2022

Permeability distribution modeling allows us to better understand and optimize production from a geothermal reservoir. However, fracture system which is the primary contributor for permeability in a geothermal reservoir are poorly understood due to the lack of data to perform fracture modelling. Natural fracture prediction (NFP) workflow is one of several approaches that can be utilized to create fracture drivers to propagate fracture model in areas where no well data exist. NFP workflow utilizes geomechanical inversion to generate the perturbed stressed around faults, then assumes that in a growing and active fault system, the orientation of fractures will be influenced by the regional tectonic stress as well as by the response of the fault movement caused by this regional tectonic stress. Basically, it will compute the heterogeneous stress around active faults through time and thereby model the orientation and density trends of the natural fractures around those faults. This study showcases the implementation of the NFP workflow to generate fracture model and permeability model in a geothermal reservoir at the Utah Frontier Observatory for Research in Geothermal Energy (FORGE) site at Milford, Utah. The Utah FORGE site is located inside the Northern Milford valley sedimentary basin with four fault systems that have been identified based on field observations, seismic reflection study, and correlation of drill logs. The geothermal systems at the Utah FORGE site is classified as hot dry rock (HDR) or enhanced geothermal system (EGS). Data used for this study are fracture well data, fault lineaments and structure, topography point data, geological map, and lithological data. The process of the workflow starts with loading all data, building models of faults and lithology, generating fracture intensity and orientation based on the NFP driver, then generating a discrete fracture model. Forward geomechanical modeling was implemented during the NFP workflow to get the stress regime based on the fault model in the field. Finally, the fracture model was created by using fracture point data set, the intensity, and orientation of fractures from the NFP process. The result of this workflow is a discrete fracture model that was upscaled into the 3D grid to get a fracture permeability model that will be very useful for a dynamic model or well targeting in the geothermal field.