Geothermal energy is rapidly becoming recognized, both in the United States and abroad, as a viable source of energy which can supplement fossil fuels for electric power generation. Exploration and development of geothermal reservoirs is intensifying in the western United States and Mexico, and will continue to expand as petroleum supplies diminish and costs increase. Although geothermal energy is commonly perceived as a new and exotic energy source, it is neither.

The San Angelo Formation is a mid-Permian sandstone and mudstone sequence about 100 feet thick that crops out in North Texas and dips westward into the Midland Basin; it is composed of two superposed members: the basal Duncan Sandstone Member and the overlying Flowerpot Mudstone Member. Depositional systems within the Duncan Member include the Copper Breaks deltaic system in the north, the Old Glory fluvial-deltaic system in the south, and the intermediate, strike-fed Buzzard Peak sand-rich tidal-flat system.

A preliminary study of the Frio sand distribution and formation temperatures and pressures was undertaken in order to define prospective areas in which a more detailed reservoir analysis is necessary prior to the selection of a site for a geothermal well.

Geologic map that depicts the surface geology of Borden, Scurry, Fisher, Martin, Howard, Mitchell, and Nolan Counties and parts of Glasscock, Sterling, Coke, Runnels, Taylor, Jones, Dawson, Martin, Lynn, Garza, Kent, and Stonewall Counties. The 6-page booklet indicates geologic formations, abbreviations, and ages.