Eastern Exmouth Plateau

Release Areas W16-9 to W16-11, Eastern Exmouth Plateau, Northern Carnarvon Basin, Western Australia

Highlights

Release Area W16-9 bids close on 23 March 2017. Release Areas W16-10 and W16-11 bids close on 8 December 2016.

  • Deep‑water gas province with multi-Tcf gas accumulations
  • Proximal to Perseus, Goodwyn and North Rankin gas accumulations, and Mutineer/Pitcairn and Exeter oil accumulations
  • Shallow to deep water depths, 130–1000 m
  • Triassic fault blocks, stacked reservoirs, variety of structural/stratigraphic trap styles
  • Large undrilled areas with potential for discovery of new plays
  • Further guidance available, please refer to 2016 Special Notices

Three Release Areas are offered on the inner Exmouth Plateau approximately 150–200 km north of Dampier (Figure 1). Release Area W16-9 comprises 15 graticular blocks and is located in a deep-water (400–1000 m) area on the eastern Exmouth Plateau. Release Area W16-10 (8 graticular blocks) lies over the Victoria Syncline within the Exmouth Plateau and extends into the southwestern margin of the Beagle Sub-basin near the Rankin Platform. It is within 15 km of the Exeter, Mutineer/Pitcairn, Hermes and Lambert oil fields in shallow waters (150–310 m).Release Area W16-11 (4 graticular blocks) extends over the Victoria Syncline from the northern Rankin Platform to the Exmouth Plateau, as defined by Geoscience Australia. It lies less than 10 km north of the Perseus, North Rankin and Goodwyn gas accumulations, in shallow water (130–260 m).

The Exmouth Plateau is a deep-water marginal plateau and is the most western 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 for many explorers on the plateau and acts as both source and reservoir. Other reservoirs include the Jansz Sandstone and sandstone units within the Barrow Group and the Brigadier Formation. 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 and stratigraphic traps of Late Jurassic (Oxfordian) and Early Cretaceous age (Figure 3).

The Rankin Platform is a northeast-trending structural high on the southeast margin of the Exmouth Plateau. It is separated from depocentres within the Dampier and Barrow sub-basins by major extensional fault systems. The Rankin Trend has been intensively explored and includes the Gorgon, Julimar, Iago, Goodwyn, Perseus and North Rankin gas fields. All of these accumulations have been sourced by fluvio-deltaic sediments within the Triassic Mungaroo Formation and Lower–Middle Jurassic sediments within the adjacent Barrow and Dampier sub-basins. The Lower Cretaceous Muderong Shale provides a regional top-seal. Intraformational claystones within the Berriasian–Valanginian Barrow Group, Forestier Claystone and equivalents, the Toarcian–Callovian Athol and Legendre formations, and the Triassic Mungaroo Formation (Figure 2) have the potential to form stacked hydrocarbon-bearing reservoirs. Several gas pipelines connect the Rankin Platform gas fields with onshore gas processing facilities at Karratha, the Ashburton North Strategic Industrial Area and Barrow Island.

Figure 4 shows the existing data coverage on the Exmouth Plateau in the vicinity of the Release Areas. Release Areas W16-10 and W16-11 have good 2D seismic coverage, with an average line spacing of less than 5 km, while coverage over W16-9 is more sparse. Several 3D seismic surveys also cover parts of each of the Release Areas.






Figures

Figure 1

Structural elements of the eastern Exmouth Plateau, adjacent Rankin Platform, and Beagle and Dampier sub-basins in the vicinity of the 2016 Release Areas, showing petroleum fields, key wells, and the 2015 and 2016 Release Areas


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Figure 2

Stratigraphy and hydrocarbon shows on the Exmouth Plateau and Rankin Platform, based on the Northern Carnarvon Basin Biozonation and Stratigraphy Chart (Kelman et al, 2013). Geologic Time Scale after Gradstein et al (2012)


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Figure 3

Selected play types on the Eastern Exmouth Plateau: a. Triassic (Rhaetian) carbonate platform/pinnacle reef play (adapted from Woodside Energy Ltd, 2011a); b. Upper Jurassic to Lower Cretaceous (Angel Formation) and Lower to Middle Jurassic (Athol Formation) fault block with inversion anticline (adapted from Woodside Energy Ltd, 2004); c. Upper Jurassic (Jansz Sandstone) stratigraphic plays (adapted from Mobil Exploration and Producing Australia Pty Ltd, 2001); d. Upper Triassic (Mungaroo Formation) tilted horst block and Upper Jurassic (Tithonian Sands) stratigraphic plays (adapted from Chevron Australia Pty Ltd, 2006); e. Upper Triassic (Mungaroo Formation) tilted fault block and Upper Jurassic (Tithonian Sands) stratigraphic plays (after BHP Billiton Petroleum Pty Ltd, 2009); and f. Upper Triassic (Mungaroo Formation) structural/stratigraphic play (adapted from Woodside Energy Ltd, 2011b). See Figure 1 for well locations


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Figure 4

Seismic and well data in the vicinity of the Release Areas on the eastern Exmouth Plateau, Northern Carnarvon Basin


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