Geothermal Resource Exploration

Abstract

Exploration for geothermal resources in the Basin and Range geomorphic province of the western United States is much akin to mineral resource exploration. In this region, potential geothermal resources are located at or near zones of intersection of normal faults, where fracture permeability permits deep circulation of meteoric water into high-temperature areas afforded by high regional heat flow. Exploration encompasses regional surveys, covering several thousand square kilometres, followed by more detailed studies of several hundred square kilometres to identify sites for deep drillholes. The most effective methods for regional exploration are geologic studies based on areal multispectral surveys, heat-flow drilling, chemical geothermometry of warm- and cold-water sources, and age-dating of rock. Detailed heat-flow-hydrologic surveys, gravity and active-seismic surveys, and geologic mapping are most effective in locating targets for deep confirmatory drilling. Geochemical-halo surveys may also be very effective in both regional and areal exploration. Results of geochemical, radiochemical, and geophysical surveys combine to furnish a comparison of long-term flow rates of geothermal systems, thereby permitting preliminary evaluation of the relative viability of the systems.