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Bedout Sub-basin

Release Area W16-8, Bedout Sub-basin, Roebuck Basin, and Broome Platform and Willara Sub-basin, offshore Canning Basin, Western Australia

Highlights

Bids close 8 December 2016

  • Underexplored region
  • Recent major oil discovery at Phoenix South 1, liquids-rich gas discovery at Roc 1
  • >21% success rate (3/14 wells) in the Roebuck Basin
  • Adjacent to the proven Northern Carnarvon Basin and Browse Basin hydrocarbon provinces
  • Shallow to deep water, 85−160 m
  • Further guidance available, please refer to 2016 Special Notices

Release Area W16-8 is located in the Bedout Sub-basin of the Roebuck Basin and extends onto the Broome Platform and Willara Sub-basin, in the offshore Canning Basin, Western Australia (Figure 1). The Release Area lies 120 km from the northwest coast of Western Australia in water depths of 85−160 m. The sub-basin is a frontier region with only 8 wells, including discoveries of oil at Phoenix South 1 and liquids-rich gas at Roc 1. No wells have been drilled in the offshore Broome Platform or the Willara Sub-basin.

The Bedout Sub-basin consists of an east-northeast to west-southwest-trending depocentre (Figure 1) filled with approximately 2.5 km of Paleozoic and 7 km of Mesozoic sediments (Smith et al, 1999). It is separated from the Beagle Sub-basin of the Northern Carnarvon Basin to the west by the North Turtle Hinge Zone, and is partly bounded to the northwest by the Bedout High. The Mesozoic succession has generally experienced only mild structuring, and thickens to the west before pinching out against, and partly draping over, the Bedout High. To the east and south the Mesozoic sediments thin and progressively onlap the older Paleozoic succession.

The Broome Platform is an uplifted area of shallow pre-Ordovician rocks (Figure 1), capped by a thin succession of Ordovician, Devonian and Permian rocks (approximately 1−2 km thick) that dip gently to the southeast (Figure 2) (Kennard et al, 1994). The offshore part of the Willara Sub-basin (Figure 1) and flanking terraces also contain a Paleozoic sedimentary succession, thought to be approximately 2 km thick based on sparse, poor quality, seismic data, although its maximum thickness is unknown. This depocentre has not been drilled, but is inferred to contain a similar succession to that intersected onshore, where the Willara Sub-basin contains an Ordovician–Devonian succession that accumulated in a series of half graben, unconformably overlain by Permian Grant Group glacial sediments (Romine et al, 1994). The Paleozoic rocks are, in turn, unconformably overlain by a Jurassic–Cretaceous succession that thickens offshore (Totterdell et al, 2014).

An active petroleum system in the Release Area is suggested by the discoveries at Roc 1 and Phoenix South 1. The presence of oil has challenged the interpretation of a predominantly gas-prone petroleum system and led to the suggestion that the Phoenix 1 well, drilled in 1980 and originally classified as a gas discovery, may actually contain significant gross oil pay. Modelling of potential Rowley and Bedout Sub-basin source rocks indicates that liquid hydrocarbons are currently being generated.






Figures

Figure 1

Structural elements of the Roebuck and offshore Canning basins, showing petroleum fields, key wells, and the 2016 Release Areas


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Figure 2

Stratigraphy, basin phases, seismic horizons and hydrocarbon shows in the Bedout Sub-basin, Roebuck Basin and the Willara Sub-basin and Broome Platform, offshore Canning Basin, based on the Canning Basin Biozonation and Stratigraphy Chart (Smith et al, 2013). Geologic Time Scale after Gradstein et al (2012)


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Figure 3

Play diagram illustrating the petroleum systems in the Bedout Sub-basin (modified from Carnarvon Petroleum Ltd, 2015)


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Figure 4

Seismic and well data in the vicinity of the Release Area in the Bedout Sub-basin, Roebuck Basin


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