Geothermal resource identification in Australia using shallow groundwater temperature data

Identifying geothermal resources typically requires time-consuming extensive geophysical surveys and deep drilling, which are costly and logistically challenging. This study illustrates the use of readily available shallow groundwater temperature data combined with surface air temperature records as a fast, low-cost, exploration screening tool for geothermal anomalies in deep sedimentary basins. The data were collated from existing piezometers used to monitor water-table fluctuations in groundwater monitoring wells, which are far more common than the bores typically used for geothermal temperature measurements. Geothermal anomalies can be identified by spatial analysis of the difference between the phreatic surface temperature and long-term averaged air temperature data. The study evaluates the workflow using known deep geothermal anomalies in two geologically distinct sedimentary basins: the onshore Perth Basin in Western Australia and the Hunter Valley in New South Wales. The analysis demonstrates that the widely available and commonly acquired hydrogeological data, along with average surface air temperature data, can be used for exploration for deeper geothermal anomalies. While the data are commonly measured to provide information about subsurface water levels, collating a more comprehensive national database of borehole temperature data would further facilitate geothermal exploration programs that are seeking deep sources of heat for electricity generation or shallow sources of heat for ground-source heat pumps.