Use of groundwater temperature data in geothermal exploration: The example of Sydney Basin, Australia

Multidimensional simulations in geothermal exploration require vast quantities of measurements, including temperature, to produce realistic estimates. In Australia, the database of temperature measurements is small, limited by sparse distribution and tainted by nonequilibrium conditions. Groundwater temperature data from the groundwater-monitoring/water-supply bore network provide a creative cost effective way to bridge the information gap. Down-hole temperature profiles are valuable when thermal equilibrium conditions are present. Equilibrium conditions are common in groundwater bores as they are installed to be long term. Effective use of groundwater temperature data for geothermal exploration requires an understanding of (1) the thermal conditions being measured, (2) the factors that affect the measurement, and (3) how the measurements can be used. Highly constrained models, rather than extrapolation maps, are the cost effective, risk-reducing solution for geothermal exploration in Australia. The Sydney Basin provides a case study of how an undervalued, 'cold' coal-bearing sedimentary basin became 'hot' through high-resolution modelling using groundwater temperature measurements. Groundwater temperature data are the new information source capable of filling the gaps left by the limited deep temperature measurements. Hydrogeological data play a critical role in geothermal exploration, as models representing a highly complex world approach reality.