Exmouth Plateau

Release Areas W16-12 to W16-21, Exmouth Plateau, Northern Carnarvon Basin, Western Australia

Highlights

Bids close for Release Areas W16-13, W16-15, W16-16, W16-19, W16-20 and W16-21 on 8 December 2016.

Bids close for Release Areas W16-12, W16-14 and W16-18 on 23 March 2017.

Prequalification for Release Area W16-17 closes on 20 October 2016, with the cash bidding auction to be held on 2 February 2017.

  • Deep‑water gas province with multi-Tcf gas accumulations
  • Proximal to Thebe, Scarborough, Io/Jansz, Pluto and Wheatstone gas accumulations
  • Shallow to ultra-deep water depths, 200–4400 m
  • Triassic fault blocks, stacked reservoirs, variety of structural/stratigraphic trap styles
  • Large frontier areas with potential for discovery of new plays
  • Further guidance available, please refer to 2016 Special Notices

A diverse range of Release Areas are offered on the Exmouth Plateau (Figure 1). These range from large areas in the underexplored western to central Exmouth Plateau to areas in mature exploration provinces that are proximal to existing fields and infrastructure. Release Areas W16-12, W16-14, W16-18, W16-20 and W16-21 are large areas (ranging from 39 to 134 graticular blocks) spanning the central to western Exmouth Plateau, in deep to ultra-deep water (900–4400 m). Release Areas W16-13, W16-15, W16-16 are on the eastern Exmouth Plateau close to the Pluto, Wheatstone and Io/Jansz gas fields in deep water (300–1500 m). W16-19 is a small Release Area of 2 graticular blocks located in deep water (1000–1100 m), 35 km northeast of the Scarborough gas field. W16-17 is a small Release Area of 2 graticular blocks surrounded by gas accumulations (including Pluto, Dionysus/Chrysaor, Julimar, West Tryal Rocks, Geryon/Eurytion, Brunello/Brulimar/Brokenwood and Urania) extending across the transition from the Rankin Platform to the Exmouth Plateau in water depths of 200–1200 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. The Triassic fluvio-deltaic Mungaroo Formation (Figure 2) has been the primary exploration target for many explorers and acts as both source and reservoir, while Upper Triassic carbonate platforms also have reservoir potential. Other reservoirs include the Jansz Sandstone and sandstone units within the Barrow Group and 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, Upper Triassic pinnacle reefs, 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 extensively explored and finds 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. Several oil discoveries have also been made on the Rankin Platform. These include the Balnaves, Eaglehawk and Egret oil fields as well as oils associated with the North Rankin, Goodwyn, Lady Nora, Keast/Dockrell and Tidepole gas fields. 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. All Release Areas have good to excellent 2D seismic coverage, while several 3D seismic surveys also cover parts of Release Areas W16-12 (Rose 3D), W16-13 (Willem-Pluto North 3D), W16-15 (Willem-Pluto North 3D), W16-16 (Io-Jansz 3D, Willem-Pluto North 3D), W16-17 (West Barrow 3D, Chrysaor 3D, Joy 3D), W16-18 (Centaur 3D, Chandon 3D, Bonaventure 3D, Scarborough HEX03A 3D) and W16-21 (Bonaventure 3D).






Figures

Figure 1

Structural elements of the Exmouth Plateau showing petroleum fields, key wells, and the 2015 and 2016 Release Areas


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Figure 2
Due to the complexity of this document and the niche scientific target audience, no alternative description has been provided. Please email Geoscience Australia at clientservices@ga.gov.au for an alternative description

Stratigraphy and hydrocarbon shows on the Exmouth Plateau 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 Exmouth Plateau: a. Triassic (Rhaetian) carbonate platform/pinnacle reef play (adapted from Woodside Energy Ltd, 2011a); b. Upper Cretaceous (Withnell Formation) fan sequence stratigraphic and Upper Jurassic (Eliassen Formation) half graben structural/stratigraphic plays (adapted from Woodside Energy Ltd, 2000); 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 Exmouth Plateau, Northern Carnarvon Basin


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