Offshore Petroleum Exploration Acreage Release 2013

Caswell Sub-basin

Location of the 2013 Release Areas W13-1, W13-2 and W13-3 in the Caswell Sub-basin of the Browse Basin.

Release Areas – W13-1, W13-2 and W13-3

Bids close – 21 November 2013


  • Adjacent to the Ichthys and Prelude gas field developments
  • Development/production plans are underway for the nearby Torosa, Brecknock and Calliance gas fields
  • Proximal to the recent gas discovery at Crown 1
  • Shallow water depths, 300–500 m
  • Numerous proven structural and stratigraphic plays
  • Excellent quality reservoirs and seals, multiple potential oil- and gas-prone source rocks and active petroleum systems within the region
  • Special Notices apply, refer to Guidance Notes

Please note that Release Area W13-1 has been amended according to Government Notices Gazette C2013G01338 (06/09/2013) to remove the part graticular block 1113. Please refer to the updated block listing and block diagram in the table below.

Release Areas W13-1, W13-2 and W13-3 are located within the Caswell Sub-basin, the northernmost depocentre of the Browse Basin, which contains up to 15 km of Paleozoic to Cenozoic sediments. The Caswell Sub-basin hosts significant discoveries of gas, condensate and, to a lesser extent, oil. Many of the fields are in advanced stages of development.

Numerous petroleum systems have been proven within the Caswell Sub-basin, with migration pathways extending east across the Prudhoe Terrace and Yampi Shelf, west to the Buffon-Scott Reef-Brecknock Anticlinal Trend and north to the Poseidon and Argus structures. Proven structural and stratigraphic plays include Upper Jurassic to Lower Cretaceous drape over erosional basement highs on the Yampi Shelf, Jurassic horsts/tilted fault blocks and associated drape anticlines, and Cretaceous submarine canyon fill, basin floor fans and 'ponded' turbidite stratigraphic traps. Organic-rich rocks with fair to moderate oil potential occur within the Plover Formation, lower and upper Vulcan formations and Echuca Shoals Formation. Gas-prone, high-quality coals and pro-delta shales occur within the Plover Formation. Four separate developments are underway: the Prelude Floating Liquefied Natural Gas (FLNG) Development, the Ichthys LNG Project, the Browse LNG Development (encompassing the Torosa, Brecknock and Calliance fields) and the Crux Gas and Liquids Project.

Related documents
Document TitlePDFOther Format
Release Area Map – Caswell Sub-basin PDF JPG
Geology – Caswell Sub-basin PDF DOC
Data Listing – Caswell Sub-basin PDF XLS
Block Listing – Caswell Sub-basin PDF DOC
Block Diagram –  Caswell Sub-basin PDF JPG
Regional Geology – Browse Basin PDF DOC
Further information on bidding and assessment PDF DOC
2013 Acreage Release Special Notices PDF DOC

Note: Due to the complexity of these figures no alternative descriptions have been provided.
Please email Geoscience Australia at for alternate descriptions.