The Geothermal Power Potential of Hot Stratigraphic Reservoirs
Rick Allis and Joseph N. Moore
Utah Geological Survey
Stratigraphic reservoirs with high permeability and temperature at economically accessible depths are attractive for power generation because of their large areal extent (> 100 km²) compared to the fault-controlled hydrothermal reservoirs (< 10 km²) found throughout much of the western U.S. A preliminary screening of the geothermal power potential of sedimentary basins in the U.S., assuming present day drilling costs, a levelized cost of electricity over 30 years of ? 10c/kWh, and realistic reservoir permeability, indicates that basins with heat flows of more than about 80 mW/m², reservoir temperatures of more than 175°C, and reservoir depths of less than 4 km are required. Such reservoirs could sustain power plants of ~100 MWe in scale. These criteria put the focus for future geothermal power generation on high heat flow regions of California (e.g., the Imperial Valley and regions adjacent to The Geysers), the Rio Grande rift system of New Mexico and Colorado (especially the Denver Basin), the Great Basin of the western U.S., and high heat flow parts of Hawaii and the Alaska volcanic arc. The two major challenges to development are the identification of the hottest basins and characterizing the permeability at economically drillable depths. The lower Paleozoic carbonate units beneath the eastern Great Basin are known to be locally very thick (up to 5 km), commonly have high permeability, and cover a very large area. This region represents the most attractive area for development of stratigraphic geothermal reservoirs.
AAPG Search and Discovery Article #90169©2013 AAPG Rocky Mountain Section 62nd Annual Meeting, Salt Lake City, Utah, September 22-24, 2013