Prospectivity

South Australia is situated between the ancient Archaean Shield of Western Australia and the mobile orogenic belts of the eastern states. As a result of this tectonic setting, the geological record in South Australia has preserved a unique history of sedimentation from the Neoproterozoic to Ordovician, and from the Early Devonian to Tertiary.

Pre-Tertiary sedimentary basins of South Australia are shown in Figure 1. State maps showing depth to magnetic basement, total magnetic intensity and Bouguer gravity are shown in Figure 2, Figure 3 and Figure 4.

The basins may be subdivided into three groups based on their relative stratigraphic position:

  • Basins of Mesozoic age which either overlie older intracratonic basins or are developed on the rifted southern continental margin of Australia. These include onshore, the Eromanga and Simpson basins in northern South Australia and the Berri Basin (Renmark Trough area). Offshore are the Bight and Otway basins, which also extend onshore, and the Polda Basin.
  • Permo-Carboniferous to Early Triassic basins which overlie early Palaeozoic basins in northern and
    southern parts of the state. These include the Cooper, Pedirka (incorporating the Eringa Trough) and Arckaringa basins in northern South Australia and the Nadda Basin (Renmark Trough area).
  • Early Palaeozoic basins of Cambrian to Ordovician age which include the Warburton, Arrowie, Stansbury and Officer basins. The last three basins are underlain by extensive Neoproterozoic sediments which are largely unmetamorphosed and thus also prospective for hydrocarbons. The Officer Basin contains a Devonian section preserved in a foreland trough setting.

The Cooper and Eromanga basins, which span NE South Australia and South West Queensland, comprise Australia’s largest onshore petroleum province. Permian and younger sedimentary basins beyond the main producing region contain similar largely non-marine sequences in intracratonic settings. Continental margin basins on and offshore have very thick Cretaceous fill and include the Otway Basin, a proven gas province. In several instances there are identified, mature source rocks for petroleum in lacustrine and marginal marine settings associated with reservoir sands. These occur not only in Permian and Cretaceous rocks, but also in basins with thick Neoproterozoic to Ordovician clastics and carbonates with additional source potential in marine settings.

South Australia has large regions of interpreted high crustal temperature associated with buried Mesoproterozoic granite intrusives at depths over 3 km, and these form important geothermal exploration targets where blanketed by insulating sediments.

Other geothermal energy plays in South Australia include:

  • hydrothermal energy from the Great Artesian Basin
  • residual heat sources in the South East around Australia’s most recently active onshore volcanoes
  • radiogenic iron oxide deposits similar to Olympic Dam and Prominent Hill, which may have even higher heat flow than the granites
  • enhanced natural thermal systems (eg Paralana Hot Springs and associated fracture zone).