A geothermal exploration corehole was drilled to a total depth of 1821.5 m on the Mountain Home Air Force Base near Mountain Home, Idaho. The corehole was used to collect an unusually large amount of data, including uniaxial compressive stress (UCS) experiments on core samples, to evaluate the geothermal potential of the western Snake River Plain. In addition, unlike many exploration holes in this region, a fluid entry was encountered at 1745.3 m and flowed artesian to the surface. A maximum temperature of 149.4 °C was calculated for the entry. A temperature log run on the corehole from 3 to 1675 m is nearly linear with little variation. The average geothermal gradient is 73 °C/km, and the average heat flow between 200 and 1500 m is 102 ± 15 mW/m2. Chemical analyses of a sample from the fluid entry suggest that a significant proportion of the water is not meteoric. Five geothermometers show equilibrium temperature in the range of 133–157 °C. Furthermore, based on the unconfined UCS experiments on basalt core samples, a brittle unit was found to comprise the fractured reservoir that the geothermal water flows from, while an overlying ductile unit acts as a hydrothermal caprock. This implies that the reservoir/caprock pair may be a target for future exploration wells drilled to delineate the extent of the potential resource and the boundaries of the connected fracture network.
Bibliographical noteFunding Information:
This work is part of Project HOTSPOT, an ARRA (American Recovery and Reinvestment Act) project funded by the US Department of Energy award EERE-0002848, the International Continental Drilling Program, and Utah State University, with additional support from the Snake Play Fairway project [US Department of Energy award (EERE-0006733)]. The authors also thank the two anonymous reviewers and Editor Inga S. Moeck, whose insights and suggestions greatly improved the final version of this work.
© 2019, The Author(s).
Copyright 2019 Elsevier B.V., All rights reserved.
- Heat flow
- Temperature log
- UCS experiments
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