Use of Rapid Temperature Measurements at a 2-meter Depth to Augment Deeper Temperature Gradient Drilling

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, it is possible to augment temperature gradient drilling with temperatures measured from a 2-meter depth. We discuss the development 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 towards thermal anomalies. As an example, a thermal anomaly related to a 60 m (200 ft) deep thermal aquifer at the Desert Queen geothermal area, near Desert Peak, Churchill County, Nevada, USA was mapped in much greater detail with 2-meter-deep measurements than possible with previous temperature gradient drilling, demonstrating that this technique can reduce the number of temperature gradient wells needed to identify zones of thermal upwelling.