Demonstration of New Geophysical Methods for Geothermal Exploration - the Technology Explained

Abstract

This paper describes a Geothermal Technology Advancement Project now underway, funded by the US Department of Energy (DE-FOA-0000522). The project advances the combined use of airborne geophysical technologies: Full tensor gradiometry (FTG) and ZTEM deep penetrating, low frequency, passive electromagnetic exploration system, set up on a combined survey acquisition platform. The combined system is currently being tested for geothermal exploration. ZTEM alone has previously been used in geothermal case studies, for example, in the Reese River region of central Nevada (Legault et al., 2010). FTG has also shown promising results as a viable tool for geothermal exploration in modelling studies in the Great Basin, central Nevada (Mataragio, 2012), and in the Salton Sea, southern California (Kohrn et al., 2011). FTG data is not currently acquired routinely for geothermal applications but this Project will highlight the benefits and advantages of its incorporation. The strengths of the key technologies which will be combined (FTG, ZTEM and Magnetics) lie in the ability to provide detailed subsurface geologic mapping by an aerial method. Such regional-scale integrated surveys for geothermal exploration will provide a better picture of the geologic framework of an area from which more focused exploration for prospective areas would be possible. Best practise will be the establishment of an interpretation toolkit aimed at reducing geological ambiguity to a much greater degree than was possible based on data from just any one of the geophysical methods alone - in particular, imagining of near vertical faults using FTG, resistive/conductive layers from ZTEM and depths from magnetics.