_ This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 228078, “Enhanced Geothermal System Propped Stimulation Greater Than 300°C: From Design to Implementation Phase I, ” by Gabrijel Grubac, SPE, Mazama Energy; Geoffrey Gullickson, SPE, Halliburton; and Alain Bonneville, Mazama Energy, et al. The paper has not been peer-reviewed. _ The complete paper provides an account of the design, implementation, and operational insights from a first-of-its-kind enhanced geothermal system (EGS) proppant stimulation targeting a dry rock setting with a bottomhole temperature of approximately 330°C. It highlights the unique challenges of creating a high-temperature EGS and the strategies employed to mitigate them, with the goal of advancing the scalability and viability of geothermal energy as a sustainable resource. Newberry Volcano Geological and Geophysical Evidence for High-Temperature EGS Development. More than 40 years of geological and geophysical investigations of the Newberry Volcano, a large active volcanic system in central Oregon, have established the presence of a substantial conductive thermal anomaly, with temperatures exceeding 320°C at 3, 000-m depth and projections of over 400°C below 4, 000 m. Importantly, this high-temperature resource occurs at relatively shallow depths and in a relatively well-characterized volcanic setting. Subsurface characterization at the site incorporates lithologic data from well logs and cuttings, which reveal variable rock properties relevant to EGS development. Several deep exploration wells have been drilled on the northwestern flank of the volcano. Davenport Newberry Holdings’ Well NWG 55-29 displays a conductive thermal regime from an approximately 1, 700-m elevation to total depth at approximately 1, 300 m. Bottomhole temperatures appear to reach 350°C. CalEnergy wells encountered temperatures greater than 315°C below 2, 740 m, although insufficient permeability prevented classification as a conventional hydrothermal resource. A 3D conceptual geologic model was originally developed during Phase 1 of the US Department of Energy’s Frontier Observatory for Research in Geothermal Energy initiative. In 2022, new gravity and wideband magnetotelluric data collection focused on undercharacterized southern regions of the caldera and south flank. The resulting data set was merged with legacy data in a joint inversion to update subsurface resistivity and density models. Well 55-29. NWG 55-29 was drilled in an area of the Newberry Volcano west flank away from any surface expressions of the caldera ring fractures mapped elsewhere. The openhole interval of the well extends between 1, 903 to 3, 066 m total measured depth. The well first intersects microcrystalline granodiorite at a measured depth of 2, 627 m. The completion approach of the well included a comprehensive design phase wherein each facet of the stimulation approach was analyzed and checked. The stimulation of this EGS well has been completed successfully, and a twin producer well has been drilled and recently stimulated with the goal of connecting the wells and enabling heat harvesting. From the application of propped stimulation greater than 300°C to running the world’s first sleeve and successfully pumping through it in the producer-well stimulation, the findings and results are an encouraging step to making superhot-rock (SHR) geothermal a scalable reality.
Chris Carpenter (Sun,) studied this question.