ABSTRACT:

The EGS (Enhanced Geothermal Systems) Collab project is performing stimulation and flow experiments in highly-monitored and well-characterized intermediate-scale (approximately10 to 20 meter) field test beds at a depth of approximately 1,500 meters in the Sanford Underground Research Facility (SURF) in the Black Hills of South Dakota. Our fracture stimulation and interwell flow tests are performed to better understand processes that control formation of effective subsurface heat exchangers that are critical to the development and success of EGS. Different EGS Collab stimulations will be performed under dissimilar stress conditions to produce data for model comparisons that better differentiate stimulation mechanisms and the evolution of permeability enhancement in crystalline rock. EGS Collab experiments provide a means of testing tools, concepts, and strategies that could later be employed under geothermal reservoir conditions at DOE's Frontier Observatory for Research in Geothermal Energy (FORGE) and other enhanced geothermal systems. Key to the project is using numerical simulations in the experiment design and interpretation of results, and the collection of high-quality stimulation/flow, thermal, geologic, and geophysical data. A wide range of geologic and geophysical data have been acquired and interpreted for pre-stimulation testbed characterization. Multiple stimulation and flow tests have been performed at SURF, and multiple data sets have been collected and analyzed during these tests including electrical resistance tomography, microseismic, continuous active source seismic monitoring, distributed temperature, and the SIMFIP tool has been used to identify fracture formation and characteristics. An overview of some of the numerical simulations and experiments performed at SURF are presented.

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