Thermal insulation and geothermal targeting, with specific reference to coal-bearing basins

Coal-bearing basins have increased economic potential for enhanced geothermal systems owing to thermal insulation provided by the coal and associated organic-rich sediments. In such insulation-dominated prospects, heat refraction effects associated with buried insulators can produce negative surface heat-flow anomalies in the most prospective areas. The Latrobe Valley in Victoria, Australia, is an archetypal coal basin. Using numerical simulations incorporating the coal geometries, we show that the Latrobe Valley coals might elevate the temperature of the rocks at 4 km depth by some 30-35°C relative to a 'base' condition with no coal. This effectively boosts the average geothermal gradient by about 30%, with a corresponding improvement in the economic case for geothermal energy in the Latrobe Valley. © 2013 © 2013 Geological Society of Australia.