ABSTRACT: Hydrocarbon Habitat of Australia's Western Margin Mesozoic Basins

PASSMORE, VIRGINIA L., and E. ANNE FELTON, Bureau of Mineral Resources, Geology and Geophysics, Canberra, Australia

Five Mesozoic sedimentary basins lie offshore along Australia's west coast: The Bonaparte, Browse, offshore Canning, Carnarvon, and Perth basins. The first four basins comprise the North West Shelf. Oil and gas have been discovered in all these basins except the offshore Canning, which has hydrocarbon shows only. Commercial oil and gas production is established in the Bonaparte, Carnarvon, and Perth basins. Australia's largest gas reserves are in the Carnarvon and Browse basins and Exmouth Plateau.

The Mesozoic basins developed as a consequence of rifting of the Australian and Indian segments of the Gondwana supercontinent during the Triassic and Jurassic. Major structural elements in the North West Shelf basins (except the offshore Canning) are similar: outer platforms, central northeast-trending grabens, and inshore shallow basement.

Potential reservoirs consist of synrift Triassic and Jurassic marginal marine and fluvio-deltaic sandstones. Most plays tested involve structural trapping, although there is potential for stratigraphic traps in sandstone wedges and beach barriers developed during delta progradation and sea level change. A Jurassic submarine fan play is newly recognized. Source and seal for Triassic and Jurassic reservoirs are provided by Jurassic marine prodelta shales. Reservoirs are also present in Cretaceous marine shelf clastics and possibly carbonates. The largest known oil and gas fields are in Triassic (Rankin Platform gas) and Cretaceous (Barrow Island oil field) reservoirs. However, several significant Jurassic accumulations, including Jabiru and Skua in the Bonaparte basin and Cossack/Wanaea in the Carnarvon basin, have been found.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)