New Geothermal Resource Delineated Beneath Black Rock Desert, Utah

Abstract

NEW GEOTHERMAL RESOURCE DELINEATED BENEATH BLACK ROCK DESERT, UTAH Mark Gwynn, Bob Blackett, Rick Allis, Christian Hardwick Utah Geological Survey PO Box 146100 Salt Lake City, UT 84114 e-mail: markgwynn@utah.gov ABSTRACT The Utah Geological Survey recently completed the drilling of ten temperature gradient wells in the Black Rock Desert of western Utah. Seven of these wells and four others drilled in the 1970s delineate a geothermal resource where temperatures of more than 150°C cover an area of about 350 km² at a depth of 3 km. This coincides with the axis of an actively extending basin containing Late Tertiary-Recent sediments up to 3 km thick overlying Mid-Late Cambrian carbonate bedrock. An area of approximately 60 km² has temperatures above 200°C at 3 km depth. An abandoned oil exploration well confirms temperatures of 230°C at 3.3 km depth in the center of this thermal anomaly. At this well, the near-surface temperature gradient is 105°C/km, and the heat flow is 125 mW/m². This thermal anomaly may be associated with a cooling intrusion in the upper crust beneath Pavant Butte volcano, which last erupted about 15,000 years ago. Potential geothermal reservoirs likely exist in the near-horizontal carbonate strata between 3 and 4 km deep in the Black Rock Desert. These same units are exposed in the adjacent Cricket Mountains west of the Black Rock Desert. If these carbonate bedrock formations are sufficiently permeable, a substantial deep geothermal resource may exist in the Black Rock Desert.