Geothermal Resource Base, Snake River Plain

Leah V. Street, Robert E. De Tar

The low to moderate geothermal resource base of the Snake River plain is extensive. Estimates of mean reservoir energy of over 455 × 10¹⁸J have been made by Mabey in 1983, and energy offset of over 26 MW thermal were made by Bloomquist et al in 1985. These low-temperature (< 150°C), hydrothermal resources are presently being used for commercial and domestic space heating and aquaculture. The thermal waters are generally high in F and NaHCO₃ constituents, but have low concentrations of dissolved solids. Consequently, most developers use the resource directly, without pretreatment.

In general, the resource is associated with the Tertiary Idavada Volcanics, a series of rhyolites and ash flow tuffs. Circulation of the thermal waters is controlled by faults, joints, and fractures. Temperatures range from 30° to 70°C, and well depths range from 800 to 3,000 ft. Most flowing wells have high yields (2,000 gpm) and shut-in pressures (250 psi).

AAPG Search and Discovery Article #91040©1987 AAPG Rocky Mountain Section Meeting, Boise, Idaho, September 13-16, 1987.