Geothermal Resources of Colorado

SP-02 Geothermal Resources of Colorado

The United States is facing a serious energy crisis. It is estimated that the electrical requirements of the United States will reach 5.8×1012 kwh by 1990. It is also estimated that the energy requirements of Colorado will grow from 11,743 Gwh in 1970 to 58,221 Gwh in 1990. Most of the future electrical power will come from conventional generating plants, however a large share will have to come from other sources such as nuclear and geothermal generating plants.

Geothermal resources — the natural heat of the earth’s interior — has been increasingly used since the start of the century to generate electricity. The present worldwide geothermal generating capacity has reached nearly 900,000 kw and will probably increase 10-fold in the near future.

The quantity of heat above surface temperature stored in the outer 62 miles (100 km) of the earth’s crust is equivalent to 2×1022 kwh, or the heat content of 3×1018 short tons of coal. The flow of heat from the earth’s interior, measured at the surface, occurs at the rate of 1.5 x 10-6 cal/cm2/sec. While most of the heat energy in the crust is too diffuse to be considered a potential resource, significant concentrations of geothermal energy do occur in local “hot spots”. Many of the anomalous high heat flow areas occur in regions that have experienced late Tertiary and Quaternary volcanism and mountain building. The deeper parts of many sedimentary basins also contain some local “hot spots”. Associated thermal springs commonly issue from faults along the margins of the volcanic areas, however some of them may be related to volcanism that occurred miles away.

Exploration for a commercial geothermal reservoir is similar to that for metalliferous mineral and hydrocarbon deposits, and involves common geological, geophysical, and geochemical techniques.

The geothermal resources of Colorado are indicated by 113 thermal springs and wells having a temperature in excess of 21°C (70°F). While these thermal springs and wells are located throughout the western half of Colorado, most of them are located in the southern Rocky Mountains of southwestern Colorado.

In 1965 Lewis (1966) measured the temperature, discharge, and specific conductance of 35 of these 113 thermal springs. From 1968-1970 Mallory and Barnett (1972) sampled and chemically analyzed 21 thermal springs and wells. Thus a total of 41 thermal springs and wells have been remeasured since 1965. The chemical analyses, temperature, and discharge of these 41 selected thermal springs and wells is presented. The temperature of the waters varies from a low of 21°C at Eldorado Springs to a high of 84°C at Hortense Hot Spring. The waters of the 41 thermal springs and wells issue from rocks ranging in age from Precambrian to Tertiary, of various composition, and under all types of geologic conditions. A brief description of the geologic conditions of the area immediately surrounding the 41 springs and wells is presented.

The 16 published surface or near surface measurements of the flow of heat from the interior of the earth in Colorado have been compiled and are given. The measurements vary from a low of 1.4 H.F.U. at Yellow Creek in the northwest part of the state to a high of 3.7 H.F.U. at Ouray, Colorado in the San Juan Mountains.

54 pages. 11 figures. 6 tables. Digital download. SP-02D.

Author: R.H. Pearl
Year: 1972