Updated Reference Discrete Fracture Network Model at Utah FORGE

Abstract

The Reference Discrete Fracture Network (DFN) model for the Frontier Observatory for Research in Geothermal Energy (FORGE) site near Milford, Utah, is used to characterize both the natural fractures present in the reservoir and induced fractures created during hydraulic stimulation. The reservoir rock consists of crystalline granitic and metamorphic rock at around 8000 ft below the ground surface. The model can be used by researchers simulating processes such as well hydraulic stimulation, local stress evolution, flow pathway analysis, circulation tests, and thermal breakthrough. Previous versions of the Reference DFN were released in 2019 and 2021 with a minor update in 2023 to include fracture planes fit to the seismic point cloud generated from the stimulation of well 16A(78)-32. The 2019 DFN version was based on data from the vertical pilot well 58-32 while the 2021 revision included data sets from vertical well 56-32 and the highly deviated well 16(78)-32. New wells in the deep geothermal reservoir rock have been drilled since the last major revision in 2021: a vertical well, 78B-32, and a second highly deviated well, 16B(78)-32, having a lateral section parallel to and 300 ft above the lateral section of well 16A(78)-32. Data sets collected from these five wells have been analyzed to further constrain fracture orientations and intensity. The current interpretation of lithologic boundaries and significant fracture zones presented in this paper relies on the application of k-means cluster analysis to wireline log data and comparison of these results with available core samples.