Development of 2-Meter Soil Temperature Probes and Results of Temperature Survey Conducted at Desert Peak, Nevada, USA

Abstract

Temperature gradient drilling has historically been a key tool in the exploration for geothermal resources in the Great Basin, USA but regulatory, environmental, and accessibility issues, as well as the expense of drilling, are increasingly limiting its use. In cases where thermal groundwater is not overlain by near-surface cold aquifers, temperatures measured at a depth of 2-meters is an efficient method for mapping thermal anomalies at a high level of detail. This is useful for augmenting deeper gradient drilling and for initial exploration of untested areas. We discuss the development and testing of a rapid, efficient, and portable 2-meter-deep temperature measurement system that obtains accurate temperatures within an hour of emplacing hollow steel probes into the ground, making it possible to map results on a daily basis so that temperature surveys can rapidly vector in towards thermal anomalies. In testing the method developed, it was possible to map in much greater detail a 60 m (200 ft) deep thermal aquifer at the Desert Queen geothermal area, near Desert Peak, Churchill County, Nevada, USA, demonstrating that this technique can reduce the number of temperature gradient wells needed to identify zones of thermal upwelling. The probes are capable of penetrating moderately rocky ground, but improvements could extend their use to very rocky or indurated ground such as caliche and silicification.