This study presents reservoir imaging progress at the Utah FORGE site by using microseismic reflections recorded by Distributed Acoustic Sensing (DAS) during circulation tests in July 2023. The imaging technique treats microseismic events as high-frequency sources, applies prestack Kirchhoff migration to each individual source, and then stacks hundreds of sources to generate a 3D reflectivity volume. Imaging results reveal the granite contact of this area and internal structures within the heart of the geothermal reservoir, which is inaccessible by typical surface arrays. By correlating with well-log data, those internal structures are likely attributed to complicated responses of mineralogical changes and natural fractures within the granitoid bedrock. Furthermore, the 3D fracture volume may delineate hydraulic fractures induced by circulation tests, enriching our understanding of reservoir dynamics and potentially enhancing geothermal exploitation strategies.

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