Evidence for Hydrothermal Convection in the Perth Basin, Australia

Abstract

There is increasing evidence for hydrothermal convection in sedimentary basins, leading to opportunities for exploitation of low temperature geothermal systems. We infer convection in the sediments of the Perth Basin of Western Australia based on two observational arguments and a theoretical one. Firstly, the fluvial sediments of the Lesueur Sandstone in the southern Perth basin show anomalously low thermal gradients. Logging from the Lake Preston 1 petroleum well shows a thermal gradient of nearly 8.7 °C/km as inferred from unequilibrated temperatures measured in the Lesueur through the depth range from 1,000 m to about 3,300 m (Figure 1). Assuming one dimensional heat conduction, Fourier’s Law is q = -k T / z, where q is vertical heat flux, k is thermal conductivity, T is temperature, and z is depth.