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Geothermal Resources of Colorado and the Potential for Electrical Power Generation

Sares, Matthew A.1; Morgan, Paul 1; Grauch, V. J.2
1 Colorado Geological Survey, Denver, CO.
2 U.S. Geological Survey, Denver, CO.

Geothermal resources in Colorado are currently used directly for pools, spas, greenhouse agriculture, aquaculture, space heating, and district-wide heating, but not for electrical power- a goal for future alternative energy resources. Several lines of evidence, including geology, groundwater geochemistry, and geophysical data, indicate that Colorado is prospective for geothermal resources suitable for electrical generation. These include:

1) High heat flow - Colorado has the second most aerially extensive heat flow anomaly in the U.S.

2) Quaternary faulting - Colorado has over 90 known faults < 1.8 Ma.

3) Neogene and younger volcanism - Colorado has over 1,200 mi2 of Neogene or younger (<22.9 Ma) volcanic deposits with five Quaternary volcanoes.

4) Rift zone tectonics - Colorado hosts the Rio Grande rift, which is prospective for geothermal resources. New aeromagnetic studies in the rift by the U.S. Geological Survey are helping to define the character of faulting and volcanic deposits.

5) A low-velocity seismic P-wave anomaly in central Colorado, the Aspen Anomaly, indicates a significant area of relatively low density and hot upper mantle. This could contribute to higher heat flow in the area.

Colorado sedimentary basins also have geothermal potential in the range of existing oil and gas wells. The Denver Basin has bottom-hole temperatures ranging between 200-250°F at roughly 10,000-11,000 ft. The San Juan Basin, south of Durango, has temperatures ranging from 150-250°F at depths between 6,500-9,000 ft. Portions of the Raton Basin west of Trinidad display high geothermal gradients.

Using data from thermal springs and wells, geothermal test holes, mineral exploration holes, and oil and gas wells, the Colorado Geological Survey has constructed statewide maps of heat flow and geothermal gradient to identify the most prospective areas for geothermal resource development. These maps help identify prospective locations for electrical power generation from conventional hydrothermal systems, as well as areas where enhanced geothermal system (EGS) technology can be applied to tap geothermal resources deeper in the earth’s crust. A recent EGS study ranks Colorado fifth among the continental U.S. states in total heat energy available below 10,000 ft deep and indicates that Colorado has more heat energy available for EGS systems in the depth range of 10,000-13,000 ft, the shallowest depth range considered by the study, than any other state in the U.S.

 

AAPG Search and Discovery Article #90090©2009 AAPG Annual Convention and Exhibition, Denver, Colorado, June 7-10, 2009