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Open-File Report 2008-1296

National Geothermal Resources—Open-File Report

A Review of Methods Applied by the U.S. Geological Survey in the Assessment of Identified Geothermal Resources

By Colin F. Williams, Marshall J. Reed, and Robert H. Mariner


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Open-File Report 2008-1296
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The U. S. Geological Survey (USGS) is conducting an updated assessment of geothermal resources in the United States. The primary method applied in assessments of identified geothermal systems by the USGS and other organizations is the volume method, in which the recoverable heat is estimated from the thermal energy available in a reservoir. An important focus in the assessment project is on the development of geothermal resource models consistent with the production histories and observed characteristics of exploited geothermal fields. The new assessment will incorporate some changes in the models for temperature and depth ranges for electric power production, preferred chemical geothermometers for estimates of reservoir temperatures, estimates of reservoir volumes, and geothermal energy recovery factors. Monte Carlo simulations are used to characterize uncertainties in the estimates of electric power generation. These new models for the recovery of heat from heterogeneous, fractured reservoirs provide a physically realistic basis for evaluating the production potential of natural geothermal reservoirs.

Version 1.0

Posted November 2008

  Also of Interest

  • USGS Fact Sheet 2008-3082, Assessment of Moderate- and High-Temperature Geothermal Resources of the United States, by Colin F. Williams, Marshall J. Reed, Robert H. Mariner, Jacob DeAngelo, S. Peter Galanis, Jr.

Suggested citation:

Williams, C.F., Reed, M.J., and Mariner, R.H., 2008, A review of methods applied by the U.S. Geological Survey in the assessment of identified geothermal resources: U.S. Geological Survey Open-File Report 2008-1296, 27 p. []

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Created: November 26, 2008
Last modified: Monday, January 30, 2009 (mfd)