Western Exmouth Plateau

Release Area W17-8, offshore Western Australia

Highlights

Bids close on Thursday 19 October 2017

  • Deep‑water gas province with multi-Tcf gas accumulations
  • Proximal to Vos, Eendracht, Brederode, Arnhem and Kentish Knock gas accumulations
  • Deep to ultra-deep water, 1400–3500 m
  • Triassic fault blocks, stacked reservoirs, reefs, variety of structural/stratigraphic trap styles
  • Proven gas in wells Alaric 1 and Cadwallon 1
  • Large lightly explored area with potential for discovery of new plays
  • This release area is considered to be lightly explored, refer to supporting infromation
  • Further guidance available, refer to 2017 Special Notices.

Release Area W17-8 (135 graticular blocks) is located over the southwestern Exmouth Plateau, in deep water of ~1400 m atop the plateau, down to ~3500 m along the base of the steep Cuvier Transform margin where it adjoins the Cuvier Abyssal Plain (Figure 1). The western part of the Release Area lies along the Cape Range Fracture Zone defining the southern flank of the Exmouth Plateau. The Vos gas field lies to the south, while the gas fields of Eendracht, Brederode, Arnhem and Kentish Knock lie to the east—all in 1000–1500 m water depths.

The Exmouth Plateau is a deep-water marginal plateau and is the most westerly of the structural elements that constitute the Northern Carnarvon Basin. The plateau is underlain by 10–15 km of flat-lying and tilted, block-faulted Paleozoic to Mesozoic sedimentary rocks, deposited during periods of extension prior to continental breakup in the Middle Jurassic and Early Cretaceous (Figure 2). The Triassic fluvio-deltaic Mungaroo Formation has been the primary exploration target on the Exmouth Plateau for many explorers and acts as both source and reservoir, while Upper Triassic carbonate platforms also have reservoir potential. Other reservoirs include the Upper Triassic Brigadier Formation, the Upper Jurassic Jansz Sandstone and sandstone units within the Lower Cretaceous Barrow Group. The Lower Cretaceous Muderong Shale forms a regional seal. Trap styles present on the Exmouth Plateau include fault-dependent closures and drapes associated with Triassic fault blocks, Upper Triassic pinnacle reefs (Exon et al, 1989), and stratigraphic traps of Late Jurassic (Oxfordian) and Early Cretaceous age (Figure 3).

The Release Area overlies a major north-northeast striking Rhaetian reef/carbonate shelf trend (Grain et al, 2013). Tiberius 1 encountered over 300 m of this limestone succession, characterised by zones of high porosity and permeability. As the succession directly overlies the deeply faulted gas-prone Mungaroo Formation, and is sealed by Lower Cretaceous marine shales, it should be considered as a major play concept.

Figure 4 shows the data coverage on the Exmouth Plateau in the vicinity of the Release Area. There is sparse coverage of 2D seismic with increased density to the east. Most of the eastern half of the Area is covered by 3D seismic survey Claudius 3D MSS. Just to the east of the Area lies 3D seismic surveys Bonaventure 3D MSS and Mary Rose 3D MSS and to the southeast lies Agrippina 3D MSS. Only four exploration wells lie within the Area (Alaric 1, Cadwallon 1, Genseric 1 and Tiberius 1) with additional stratigraphy provided by Vos 1, to the south, and Eendracht 1 and Brederode 1, to the east.