--> ABSTRACT: Geochemical Evidence for Numerous Mesozoic Petroleum Systems in the Bonaparte and Browse Basins, Northwestern Australia, by Dianne S. Edwards, John M. Kennard, James C. Preston, Christopher J. Boreham, Roger E. Summons, and John E. Zumberge; #90906(2001)

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Dianne S. Edwards1, John M. Kennard1, James C. Preston2, Christopher J. Boreham3, Roger E. Summons4, John E. Zumberge5

(1) Australian Geological Survey Organisation, Canberra, ACT, Australia
(2) BHPP, Melbourne, Australia
(3) Australian geological Survey Organisation, Canberra, Australia
(4) Australian Geological Survey, Canberra, Australia
(5) GeoMark Research, Inc, Houston, TX

ABSTRACT: Geochemical Evidence for Numerous Mesozoic Petroleum Systems in the Bonaparte and Browse Basins, Northwestern Australia

After twenty years of active exploration in the Bonaparte Basin geoscientists are yet to come to an adequate understanding of the regions active petroleum systems. In this study, a common set of geochemical parameters was measured for all known producing fields and shows in the region and the results analysed using statistical methods. This approach revealed the existence of at least nine distinct oil families. Two of the nine oil families correspond to those of the Paleozoic fluids of the Larapintine and Gondwanan Supersystems in the Petrel Sub-basin. The Upper Jurassic, Lower Vulcan Formation within the Swan Graben has sourced the majority of oils produced from the Vulcan Sub-basin. In ZOCA, three distinct oil families are recognised: The first family encompasses hydrocarbons generated from mixed marine and terrestrial organic matter deposited in the Jurassic-Cretaceous Plover, Elang, Frigate formations and Flamingo Group. A second ZOCA oil family includes condensate from Sunrise-1 which has a marine carbonate biomarker signature. A third group of oils is reservoired in fractured Darwin Formation and has a marine geochemical signature; these oils appear to be expelled from the Cretaceous Echuca Shoals Formation and are geochemically related to the Browse Basin Cornea and Gwydion oils. Finally, there are three families of oils with dominant terrestrial organic matter contents that are disbursed over the Browse and Bonaparte Basins and in the transition zone. One of these families can be mapped to the Early-Middle Jurassic Plover formation. This system is the least understood but its wide geographic distribution suggests that it has unrealised potential. An important geochemical outcome of the study is a corroboration of biomarker assignment of oil families by n-alkane carbon isotopic analysis. Isotopes also assist in identifying associated and non-associated gas.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado