Abstract

In the past 5 years, oil exploration in Australia has been greatly accelerated, but no commercial fields have been discovered. Exploration has been most intense in Western Australia, though active work has been carried out in every other Australia state except Tasmania. Precambrian sedimentary, metamorphic, and intrusive rocks cover a large part of Australia. During the Paleozoic, a huge volume of sediments accumulated in the great Tasman geosyncline, along the eastern side of the present Australian continent. The geosyncline underwent several major orogenies the last of which occurred in the late Permian. Since then the continent has been remarkably stable, without any widespread orogenic movements. The pre-Permian sediments of the Tasman geosyncline are generally regarded as basement in oil exploration as they are metamorphosed and intensely deformed. In the central and western parts of the continent, the Precambrian shield is overlapped by a series of basins containing Cambrian and younger sediments. In eastern Australia, similar basins overlie basement rocks of the Tasman geosyncline, and contain Permian and younger sediments. These basins show relatively mild deformation, and several are regarded as prospective in oil exploration. The Carnarvon and Canning basins in Western Australia are believed to contain thicker prospective sedimentary sequences, and consequently are likely to have better oil prospects, than the other sedimentary basins of Australia. For this reason, they have recently received most attention in oil exploration. However, several other basins are regarded as promising and are being tested by Australian and overseas companies. The only bore drilled in Australia which has produced a significant flow of oil is West Australian Petroleum's Rough Range No. 1 in the Carnarvon Basin. However, the oil accumulation beneath this well is believed to be too small for commercial exploitation. Shows of oil have been reported from bores in several other Australian sedimentary basin but these have not been followed by discoveries of commercial value.

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