PASSMORE, VIRGINIA L., and * PAUL E. WILLIAMSON, Bureau of Resource Sciences, Parkes, ACT, Australia; and ALLAN R. GRAY, Queensland Department of Minerals and Energy, Brisbane, Queensland, Australia

ABSTRACT: An Unexplored Jurassic Plan in the Carpentaria Basin of Australia and Papua New Guinea

This study has indicted an unexplored Jurassic play in the eastern Carpentaria basin in Australian territorial waters and extending into Papua New Guinea territorial waters.

The Carpentaria basin has been spasmodically explored over the last 35 years but offshore has sparse seismic data and only one well which encountered Proterozoic rhyodacite basement without encountering the target reservoir section. The present study suggests that an equivalent of the Toro Sandstone, the main reservoir in Papua New Guinea, occurs in the Carpentaria basin. The Toro Sandstone is a Late Jurassic marginal marine sequence deposited during a period of low sea level. In the Carpentaria basin, the equivalent sandstone, the Gilbert River Formation, is an intermediate marine sandstone with good reservoir properties. It is overlain by the Rolling Downs Group, a regional mudstone seal.

Source rock in the Carpentaria basin might occur in the underlying Jurassic Garraway beds and may be mature in the Carpentaria Depression. However, less than 1800 m of sediment is present within the offshore Carpentaria basin. This study has delineated for the first time the underlying Bamaga basin containing up to 3 km of pre-Jurassic sediment and multiple exploration leads. Possible direct hydrocarbon indicators in seismic data of the Carpentaria basin suggests that hydrocarbons formed in the Bamaga basin may have migrated vertically into faulted or drape anticlinal structures in the Carpentaria basin.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.