This report presents an overview of basin architecture, tectonic evolution and lithostratigraphy and is the first part of a series of reports reviewing various aspects of the petroleum prospectivity of the Cooper Basin.
Structural architecture, formation extent and thickness is characterised through construction of a regional 3D geological model, designed to capture the formations associated with the major play types in the basin. Existing published Cooper Basin horizons are integrated with formation tops and new seismic data interpretations, ensuring seamless integration of datasets across the state border.
The late Neoproterozoic to Cenozoic evolution of the Cooper Basin region is discussed in the context of the broader tectonic evolution of eastern Australia. In addition, stratigraphy ages have been updated to produce a revised Cooper Basin stratigraphic chart, consistent with the 2012 Geological Time Scale and updated spore pollen age calibration. The new formation ages, along with the timing of key tectonic events and regional erosion estimates, are assigned to the 3D geological model, enabling extraction of time-slice cross-sections through the basin, capturing the regional burial history of the Cooper-Eromanga-Lake Eyre succession
Isopachs extracted from the 3D model are used to review the extent and thickness of each formation. The Permian Toolachee and Patchawarra formations in Queensland are shown to have a wider extent compared with previous studies. In addition, the boundaries of Roseneath and Murteree shales were revised, although their distribution still remains uncertain in areas such as the Arrabury Depression.
Lithofacies analysis published for South Australia are integrated with new electrofacies mapping results in Queensland to produce the first basin wide set of lithofacies maps for the Toolachee, Daralingie, Epsilon and Patchawarra formations. The resulting net sand, silt, shale and coal thickness maps characterise the regional distribution of key source, reservoir and seal intervals across the basin. Maps of net coal and shale thickness clearly demonstrate an abundance of potential source rock facies in the Toolachee and Patchawarra formations in all regions. Additional potential source rock facies can be found in the Roseneath and Murteree shales and coals and shales of the Daralingie and Epsilon formations. Net sand thickness maps highlight possible reservoir facies distribution.
This study presents the most detailed regional 3D geological model published for the Cooper Basin to date. The model is designed to characterise the formations associated with the basin's key petroleum systems elements, providing a framework for future regional scale petroleum systems analysis and resource assessment studies. While this work provides important insights into both the conventional and unconventional hydrocarbon prospectivity of the basin, it also has application for the assessment of other resources such as groundwater.
