THE AGE DISTRIBUTION OF PETROLEUM IN AUSTRALIA

Abstract

Although significant reserves of petroleum have been located in relatively few Australian provinces, when the host rocks of all Australian discoveries are plotted against geological time, there are few systems which do not contain reserves. When geochemical indications are included, Australia has a capacity to yield hydrocarbons from rocks as old as the Middle Proterozoic. When reserves are considered in terms of tectonic events, mid-Carboniferous, Late Triassic, mid-Jurassic and Late Cretaceous-Cenozoic phases of deformation have been responsible for the bulk of the petroleum traps. The least understood of these phases, that in the Cenozoic, was quantitatively the most significant in that it largely controlled trap formation in the Gippsland, Surat, Otway, Cooper, Eromanga and Carnarvon Basins. Reservoirs are dominantly in siliciclastic rocks deposited in environments ranging from alluvial to shelfal marine. The climatic and tectonic histories of the continent have resulted in it being more gas-prone than world averages.