Geothermal exploration in the Western United States

Abstract

Over 90 percent of geothermal phenomena in the United States are in 13 western states, comprising more than 1000 warm and hot spring and fumarole localities. Some 100 can be considered hyperthermal. Exploration in these areas has been of two types: incidental and directed. Incidental exploration has included geologic studies and drilling in thermal areas for purposes other than geothermal development. The Salton Sea. California, geothermal field was explored initially in this manner. Directed exploration has included geological, geophysical, and geochemical methods, and has resulted in geothermal test drilling in six states. At least six produceable fields have been discovered: The Geysers, California; Salton Sea. California: Casa Diablo, California: Beowawe. Nevada: Brady's Hot Springs, Nevada: and Yellowstone National Park. Wyoming. Reservoir base temperatures exceed 200°C probably at all of these fields. The Geysers produces dry steam; Salton Sea produces brine: the others produce hot water. Only at The Geysers is electric power being generated: 83,000 kW of capacity has been installed, and facilities for an additional 110,000 kW are being constructed. At Salton Sea there is limited commercial production of calcium chloride from geothermal brine. Many insufficiently explored areas and marginal fields warrant additional directed exploration. These include: Surpise Valley, California; the Carson Sink, Nevada; the high Cascade Range in California, Oregon, and Washington; Valles Caldera, New Mexico; parts of the Aleutian Islands, Alaska; and the island of Hawaii. At least two geothermal prospects, Clear Lake, California, and Steamboat Springs, Nevada, have been abandoned because of problems of waste-water disposal and plugging of wells. These problems are encountered at other fields, including Salton Sea and Casa Diablo. Heat exchanging may provide a means to utilize these marginal fields. Several localities use geothermal water for space heating: outstanding of these is Klamath Falls, Oregon.