Browse Basin

The Browse Basin covers an area of approximately 140,000 km2 and lies entirely offshore, north of Broome. The basin is bounded by the Leveque Shelf in the south, the Kimberley Block to the east, and the Ashmore Platform and Scott Plateau in the north, and grades into the offshore Canning Basin to the southwest. The area can be serviced from Broome and Derby, which have port and air facilities.

The economics of development operations in the Browse Basin are often adversely affected by the isolation of the area and by the fact that the majority of the basin lies in waters more than 200 m deep. Currently the only State interests in the Browse Basin are associated with the Torosa gasfield over Scott Reef as it has Retention Leases TR/5 (regulated under the Petroleum (Submerged Lands) Act 1982) and R2 (regulated under the Petroleum and Geothermal Energy Resources Act 1967).

The recent discovery of small islands in the Scott Reef area by Geoscience Australia has led to a revision of the boundaries between WA and Commonwealth jurisdictions, resulting in the WA administered area increasing in size.

For information on the commonwealth areas of the Browse Basin see Geoscience Australia website.

Geological setting

Jackup drilling in the Browse Basin (courtesy of Woodside Energy)
Jackup drilling in the Browse Basin (courtesy of Woodside Energy)

The Browse Basin, which forms part of the Westralian Superbasin, is a northeast-trending depocentre containing up to 15 km of Paleozoic to Cenozoic sediments. The oldest sediments in the basin, assumed to be Permian in age, are identified along the southeastern basin margin in the Rob Roy 1 and Yampi 1 wells, suggesting that sedimentation commenced during rift initiation along the North West Shelf.

The sedimentary succession of the Browse Basin is divided into two episodes, Late Permian to Jurassic, and Late Jurassic to Cenozoic, with a regional Jurassic unconformity terminating the first episode. The sediments below this unconformity are substantially block-faulted and buried to approximately 4000 m.

Exploration history

Exploration commenced in the Browse Basin in 1967, when Burmah Oil Company Australia Ltd (BOCAL, now Woodside) acquired 1600 km of regional seismic data. Since that time, over 180,000 km of 2D and 46,000 km2 of 3D seismic data has been acquired, some of which is now on open file.

The fourth well drilled in the basin, Scott Reef 1 (completed in 1971), was significant in discovering Australia’s potentially largest gasfield (now named Torosa). Since then, more than 105 wells have been drilled and there have been over 20 hydrocarbon discoveries. Recent discoveries include the Toccata, Fortissimo, Ichthys North, Ichthys West, Poseidon, Mimia, Burnside, Kronos, Boreas, Proteus, Zephyros, Crown and Lasseter wells.

Petroleum prospectivity

Although the Browse Basin has had limited exploration, the hydrocarbon discovery rate is extremely favourable. Reservoirs are identified at depths of between 4000 and 5000 m, or between 3000 and 3500 m on the basin margins, where stratigraphic play concepts may be valuable. Several structures and potential stratigraphic plays remain undrilled in the basin. The logistics of operating in such a remote area and within deep water are major hindrances to economic discoveries. As such, the Browse Basin is considered both a high-risk and high-reward area.

Find out more about the geological setting and exploration history of the Browse Basin (page 32)