Thermal modelling of the hot dry rock geothermal resource beneath GEL99 in the Cooper Basin, South Australia

Abstract

The aim of this project was to estimate the distribution of temperature within the crystalline basement beneath Geothermal Exploration Lease GEL99, in the Cooper Basin, South Australia. The purpose was to constrain the energy potential (and economic value) of the underlying hot dry rock geothermal resource. One-dimensional conductive heat flow models were constructed for 12 wells in the vicinity of the permit. The models utilised temperature and lithological information derived from petroleum industry boreholes. Results indicate that surface heat flow is close to 100 mW/m2 across much of GEL99, with some localised variation near the Big Lake gas field. The relationship between surface heat flow and basement depth suggests that heat is generated in the underlying granite at a rate of about 10 µW/m3. The high basement heat generation explains the relatively high surface heat flow. Vertical conductive heat flow was extrapolated into the basement underlying each well in order to predict the temperature profile. Results suggest that the highest basement temperatures are in the vicinity of Moomba North 1, where the temperature may exceed 260°C at a depth of 5 km.