Numerical Modelling of the Sydney Basin Using Temperature Dependent Thermal Conductivity Measurements

Abstract

The Thermal structure of continental crust is a critical factor for geothermal exploration, hydrocarbon maturation and crustal strength, and yet our understanding of it is limited by our incomplete knowledge of its geological structure and thermal properties. One of the most critical parameters in modelling upper crustal temperature is thermal conductivity, which itself exhibits strong temperature dependence. In this study, finite-element geothermal models of the Sydney Basin are generated through the use of deal.II finite element libraries. Basin geometry and structure is adapted from Danis, et al. (2011), which quantified the extent of Triassic sediment, Permian coal measure, Carboniferous volcanics and Basement thickness. We find that temperature-dependent thermal conductivity result in lower lateral variation in temperature compared to constant thermal conductivity models. However, the average temperatures at depth are significantly higher when temperature-dependent thermal conductivity effects are included. A number of regions within the Sydney Basin demonstrate temperature above 150C at depths of less than 2000m in these models, for instance NW of Singleton exhibits a strong thermal anomaly, demonstrating the potential for geothermal prospectivity of the region from experimentally-constrained thermal parameters. Future work will address the repeatability and application of this type of thermal model in areas of varying geology and stratigraphy, as well as refining the model by adding new variables, such as pressure or fine tuning existing variables.