| Abstract |
Surface conductive heat flux theoretically provides the most direct evidence of the existence, location and extent of a buried concentration of geothermal energy because it is governed by the same potential field mathematics that describes gravity, magnetics and electromagnetic geophysical techniques. Geothermal reservoirs theoretically generate measurable surface heat flux anomalies. This fact underpins the use of 'heat flow wells' to confirm a heat source before appraisal drilling for deep hydrothermal systems. Heat flow wells are, however, expensive to drill, which precludes their use as a routine exploration tool to detect and delineate geothermal reservoirs. This paper provides an update on the development of one meter long probes that can be deployed at relatively little cost across an entire geothermal prospect area, and which measure conductive surface heat flux. Field trials in Australia and Mexico (and planned for New Zealand) have demonstrated the tool's ability to quantify conductive surface heat flux to an accuracy and precision of about ± 50 mW/m2. Clear variations in surface heat flux on the order of W/m2 have been delineated over known hydrothermal systems, demonstrating the potential to map the distribution of subsurface heat at regional scale. The tool shows great promise to improve exploration efficiency by identifying areas with high concentrations of sub-surface heat prior to appraisal drilling. |