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The Evolution of Well 58-32 at Utah FORGE in Response to Fluid Flow Along a Stimulated Fracture Corridor
Stuart SIMMONS, Clay JONES, Tobias FISCHER, Peter MEIER, Joe MOORE
[Energy & Geoscience Institute, University of Utah, USA]
Well 58-32 was completed in September 2017, providing confirmation of a hot dry granitic rock reservoir at drillable depths that advanced development of the Utah FORGE field laboratory. Apart from small scale injection testing in 2019, the well was used for the temporary deployments of geophone strings and seismic monitoring during drilling and stimulation operations related to the completion of wells 16A(78)-32 and 16B(78)-32. In this early phase of EGS reservoir development through to at least 2022, the water levels in 58-32 were relatively static, and the water composition showed a moderate increase in total dissolved salts compared to the culinary grade water with which it was originally filled. Further compositional evolution occurred by 2024, which is believed to be related to stimulation of stage 9 in 16A(78)-32. The associated sharp pressure rise led to removal of geophones, and at the start of the four-week circulation test in August 2024, vigorous gas bubbling was noticed. The well was shut in, and a flow line was added to sample and monitor fluids safely. When subsequently opened for short periods to acquire samples, a frothy two-phase fluid discharged, and chemical analyses indicated the well water had transformed into a carbon dioxide rich saline solution. Furthermore, connection had been made with the Utah FORGE reservoir, 200 m away. Separately, temperature logs show that the conditions remained unchanged from its original conductive gradient. In this report, an overview of changes in 58-32 fluid chemistry, including results of recent downhole sampling, are described. Provisionally, these data provide clues regarding the character of fluids occupying the periphery of stimulated fractures in the Utah FORGE EGS reservoir.
Topic: Enhanced Geothermal Systems