Is it hot enough down there? Assessing geothermal potential in the Sydney-Gunnedah-Bowen Basin

Abstract

The Earth?s upper crust hosts many important economic resources, from minerals to groundwater to energy, but the subsurface structure and associated thermal structure is poorly understood. Internal heat is the driving force behind many of the Earth?s processes and is now being considered as a new form of clean renewable energy. High resolution 3D thermal models, incorporating detailed geological structure and real world data, are effective in assessing thermal structure and provide improved temperature estimates for geothermal exploration. Unlike historical 1D models and extrapolated temperature at depth maps, 3D thermal models are appealing to the geothermal exploration industry as they are not limited by the sparse nature of down-hole temperature measurements or heat flow and the uncertainties of such models can be calculated. In the Sydney-Gunnedah-Bowen Basin (SGBB) system, Australia?s energy rich sedimentary basin, the thermal structure is poorly understood resulting in its geothermal potential largely being ignored. Thermal modelling using optimised parameters shows estimated temperatures at 5km below the surface, the economic limit of drilling, to range from 120°C to 240°C, with highest temperatures under thick sediments with multiple insulating coal layers. Using the 150°C temperature contour as in indicator for potential geothermal prospectivity, the most potential basins are in the Bowen and Sydney.