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Barcoo Sub-basin

Release Area W16-5, Barcoo Sub-basin, Browse Basin, Western Australia

Highlights

Bids close 23 March 2017

  • Under-explored area containing similar source rocks, reservoirs, seals and plays as the adjacent Caswell Sub-basin petroleum province
  • Adjacent to the Brecknock and Calliance gas fields to the north
  • Gas shows in wells south of the release area
  • Some 3D seismic coverage over the release area
  • Further guidance available, please refer to 2016 Special Notices

Release Area W16-5 is located within the Barcoo Sub-basin, the southernmost depocentre of the Browse Basin, 190 km off the northwest coast (Figure 1) in water depths of 140–1400 m. Compared to the Caswell Sub-basin, this region is underexplored. The release area covers 34 graticular blocks (2810 km2) and is adjacent to the Brecknock and Calliance gas fields to the north. There are also gas shows in the Arquebus 1, Lombardina 1 and Sheherazade 1 wells to the south.

The Browse Basin is one of a series of extensional basins that form the Westralian Superbasin and has undergone six major tectonic phases during its development. This includes middle Carboniferous–early Permian extension; early Permian to Late Triassic thermal subsidence; Late Triassic to Early Jurassic inversion; Early to Middle Jurassic extension; Late Jurassic to Cenozoic thermal subsidence; and Middle Miocene to Holocene inversion (Figure 2).

The Barcoo Sub-basin forms one of the major depocentres of the Browse Basin, and is 200 km long (northeast–southwest) and 130 km wide (northwest–southeast) and contains up to 12 000 m of Paleozoic to Cenozoic sediments (Struckmeyer et al, 1998; Figure 2). The most likely source for hydrocarbons in this sub-basin is the Lower to Middle Jurassic Plover Formation, which is the source and host of dry gas occurrences in the adjacent Brecknock and Calliance gas fields. At the Brecknock and Calliance accumulations, the upper Plover Formation is the main reservoir, while the lower Plover Formation acts as the main reservoir at Torosa (Figure 2). The older sandstones were deposited in a fluvial-dominated upper delta plain, with the younger sandstones reflecting deposition in a tidally influenced lower delta plain environment (Tovaglieri et al, 2013; Tovaglieri and George, 2014). Some tuffaceous volcanics are also present at some locations within the lower Plover Formation (Tovaglieri et al, 2013).

Combined structural and stratigraphic plays include Jurassic horsts/tilted fault blocks and associated drape anticlines (Figure 3), and Cretaceous submarine canyon fill and basin floor fans. Miocene fault-reactivation inversion anticlines along the margin of the Barcoo Sub-basin and Leveque Shelf also provide structural traps (e.g. Lombardina structure drilled by the Arquebus 1, Lombardina 1 and Sheherazade 1 wells; South Galapagos 1 anticline; Figure 3).

Figure 4 shows the existing data coverage of the region, with only one well, Omar 1, being located within the Release Area. 2D seismic coverage has an average 5 km line spacing in the Release Area. The Brecknock 3D (to the north) and Omar 3D (to the south) seismic surveys overlap parts of the Release Area.






Figures

Figure 1

Structural elements of the Barcoo Sub-basin in the vicinity of the 2016 Release Area, showing petroleum fields, key wells, and the 2016 Release Areas


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Figure 2

Stratigraphy and hydrocarbon shows in the Barcoo and Caswell sub-basins based on the Browse Basin Biozonation and Stratigraphy Chart (Kelman et al, 2014). Geologic Time Scale after Gradstein et al (2012)


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Figure 3

Play types in the vicinity of the Release Area in the Barcoo Sub-basin, Browse Basin


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Figure 4

Seismic and well data in the vicinity of the Release Area in the Barcoo Sub-basin, Browse Basin


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