Geologic characteristics of Valles Caldera geothermal system in New Mexico

The Valles Caldera is in north-central New Mexico, 60 mi (97 km) north of Albuquerque. The caldera is a prominent geologic structure in the Jemez Mountains, a complex volcanic highland of Pliocene and Pleistocene age. Surficial evidence of geothermal resources includes the widespread distribution of rhyolitic volcanic in space and time, large areas of hydrothermally altered rock, and hot springs and gas seeps. Nineteen geothermal wells have been drilled in the caldera. The principal geothermal resource discovered is a liquid-dominated, under-pressured system with base temperature in excess of 260 degrees C, and salinity on the order of 6,000 ppm total dissolved solids. A maximum temperature of 330 degrees C has been measured. Some wells have encountered a vapor-dominated reservoir overlying the liquid-dominated reservoir. Production is principally from fractures in the lower part of the rhyolitic Bandelier Tuff. Typical wells are 5,000 to 9,000 ft (1,525 to 2,745 m) deep.