About This Item

Share This Item

The AAPG/Datapages Combined Publications Database

AAPG Bulletin

Abstract

AAPG Bulletin, V. 106, No. 6 (June 2022), P. 1213-1237.

Copyright ©2022. The American Association of Petroleum Geologists. All rights reserved.

DOI: 10.1306/12162120148

A very unconventional hydrocarbon play: The Mesoproterozoic Velkerri Formation of northern Australia

Grant M. Cox,1 Alan S. Collins,2 Amber J. M. Jarrett,3 Morgan L. Blades,4 April V. Shannon,5 Bo Yang,6 Juraj Farkas,7 Philip A. Hall,8 Brendan O’Hara,9 David Close,10 and Elizabeth T. Baruch11

1Tectonics and Earth Systems (TES) Group, Department of Earth Sciences, The University of Adelaide, Adelaide, South Australia, Australia; [email protected]
2TES Group and Mineral Exploration Cooperative Research Centre (MinEx CRC), Department of Earth Sciences, The University of Adelaide, Adelaide, South Australia, Australia; [email protected]
3Northern Territory Geological Survey, Darwin, Northern Territory, Australia; [email protected]
4TES Group, Department of Earth Sciences, The University of Adelaide, Adelaide, South Australia, Australia; [email protected]
5TES Group, Department of Earth Sciences, The University of Adelaide, Adelaide, South Australia, Australia; [email protected]
6TES Group, Department of Earth Sciences, The University of Adelaide, Adelaide, South Australia, Australia; [email protected]
7TES Group and MinEx CRC, Department of Earth Sciences, The University of Adelaide, Adelaide, South Australia, Australia; [email protected]
8TES Group, Department of Earth Sciences, The University of Adelaide, Adelaide, South Australia, Australia; [email protected]
9Santos Limited, Adelaide, South Australia, Australia; Brendan.O’[email protected]
10Santos Limited, Adelaide, South Australia, Australia; present address: Tamboran Resources, Brisbane, Queensland, Australia; [email protected]
11Origin Energy Ltd., Brisbane, Queensland, Australia; [email protected]

Abstract

The ca. 1.5–1.3 Ga Roper Group of the greater McArthur Basin is a component of one of the most extensive Precambrian hydrocarbon-bearing basins preserved in the geological record, recently assessed as of 429 million bbl oil (68 million cubic meters of oil) and between 8 and 118 TCF (222.56 billion cubic meters) of gas (in place). It was deposited in an intracratonic sea, referred to here as the McArthur-Yanliao gulf.

The Velkerri Formation forms the major deep-water facies of the Roper Group. Trace metal redox proxies from this formation indicate that it was deposited in stratified waters, in which a shallow oxic layer overlay suboxic to anoxic waters. These deep waters became episodically euxinic during periods of high organic carbon export. The Velkerri Formation has organic carbon contents that reach ∼10 wt. %. Variations in organic carbon isotopes are consistent with organic carbon enrichment being associated with increases in primary productivity and export, rather than flooding surfaces or variations in mineralogy.

Although deposition of the Velkerri Formation in an intracontinental setting has been well established, recent global reconstructions show a broader mid to low latitude gulf, with deposition of the Velkerri Formation being coeval with the widespread deposition of organic-rich rocks across northern Australia and northern China. The deposition of these organic-rich rocks may have been accompanied by significant oxygenation associated with such widespread organic carbon burial during the Mesoproterozoic.

Pay-Per-View Purchase Options

The article is available through a document delivery service. Explain these Purchase Options.

Watermarked PDF Document: $14
Open PDF Document: $24

AAPG Member?

Please login with your Member username and password.

Members of AAPG receive access to the full AAPG Bulletin Archives as part of their membership. For more information, contact the AAPG Membership Department at [email protected].