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Exmouth Plateau

W15-13, W15-16 and W15-17: bids close 29 October 2015
W15-14: bids close 21 April 2016

  • Deep‑water gas province with multi-Tcf gas accumulations
  • Proximal to Thebe, Scarborough and Io/Janz gas accumulations
  • Shallow to deep water depths, 80–1200 m
  • Triassic fault blocks, stacked reservoirs, variety of structural/stratigraphic trap styles
  • Large undrilled areas with potential for discovery of new plays
  • Special Notices apply, refer to Guidance Notes

A diverse range of Release Areas are offered on the Exmouth Plateau and Rankin Platform (Figure 1). Release Area W15-13 comprises 2 graticular blocks and is located in shallow water (80–150 m) on the Rankin Platform, adjacent to the Wheatstone and Iago gas fields. Release Area W15-14 is a large (30 graticular blocks), deep-water area on the eastern Exmouth Plateau, approximately 30 km north of the Goodwyn, Perseus and North Rankin gas fields. Release Area W15‑16 is located over the axis of the Kangaroo Syncline, on the inboard Exmouth Plateau, approximately 170 km north of the town of Exmouth. It is close to the giant Io/Jansz gas field and on trend with the Satyr gas discoveries to the southwest. Release Area W15-17 is located on the western Exmouth Plateau, adjacent to the giant Scarborough gas accumulation and approximately 250 km offshore.

The Exmouth Plateau is a deep-water marginal plateau and is the most western of the structural elements that comprise 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 on the plateau and acts as both source and reservoir. 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 and stratigraphic traps of Late Jurassic (Oxfordian) and Early Cretaceous age.

The Rankin Platform is a northeast-trending structural high on the southeast margin of the Exmouth Plateau (Figure 3). It is separated from depocentres within the Dampier and Barrow sub-basins by major extensional fault systems. The Rankin Trend has been intensively explored (Figure 4) 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. Intra-formational 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.

Petroleum systems elements

Exmouth Plateau and Rankin Platform

Sources Exmouth Plateau and Rankin Platform
  • Triassic fluvio-deltaic sediments of the Mungaroo Formation (gas-prone)

Rankin Platform

  • Lower–Middle Jurassic marine and deltaic Murat Siltstone and Athol and Legendre formations (gas-prone but early mature)
Reservoirs Exmouth Plateau and Rankin Platform
  • Middle–Upper Triassic fluvio-deltaic to marginal marine Mungaroo Formation

Exmouth Plateau

  • Lower Cretaceous basin-floor fans and turbidites in the Barrow Group
  • Upper Jurassic upper–lower shoreface Jansz Sandstone
  • Upper Triassic carbonate reefs (no discoveries to date)
  • Upper Triassic shallow marine-deltaic Brigadier Formation
Seals Regional seal
  • Lower Cretaceous marine claystones of the Muderong Shale

Intraformational seals

  • Lower Cretaceous distal marine claystones of the Barrow Group (Forestier Claystone equivalents)
  • Upper Jurassic condensed marls and claystones of the Dingo Claystone
  • Intra-formational fluvio-deltaic claystones of the Mungaroo Formation
Traps Exmouth Plateau and Rankin Platform
  • Tilted Triassic fault blocks and associated drapes
  • Lower Cretaceous basin-floor fan stratigraphic traps

Exmouth Plateau

  • Upper Jurassic shoreface sandstone stratigraphic traps
  • Upper Triassic pinnacle reefs (unproven)

Infrastructure and markets

The Release Areas are proximal to identified multi-Tcf gas fields, several recent discoveries and to established LNG projects. Additional infrastructure associated with new LNG developments is currently under construction. Release Area W15-13 is located within 8 km of the Pluto LNG Export Pipeline.

Critical risks

The absence of gas charge is not considered to be an exploration risk on the Rankin Platform. Within Release Area W15-13, trap integrity, and reservoir distribution and quality constitute the primary exploration risks. Reservoir quality is generally greater in the shallower Triassic reservoirs. For Upper Jurassic and younger deep-water, basin-floor fan sand and turbidite plays, the distribution of reservoir quality sandstones within these fine-grained deposits can be problematic.

The full areal extent of the petroleum system(s) present on the northern and western parts of the Exmouth Plateau has yet to be determined. Continued exploration success on the Exmouth Plateau will be dependent on the delineation of competent traps that have access to charge from the gas‑prone Mungaroo Formation. Seismic and well data indicate that traps tested by several wells drilled on the northern Exmouth Plateau have been breached (e.g. Jupiter 1). Trap breach is a significant exploration risk on the northern part of the plateau and is a possible explanation for the occurrence of hydrocarbon bearing structures on the northern Exmouth Plateau that are not filled to spill point (Longley et al, 2002).

Data sets

Wells Data and Seismic Survey listings for the Rankin Platform and Exmouth Plateau are available on the Supporting Information page.

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ADAMSON, K.R., LANG, S.G., MARSHALL, N.G., SEGGIE, R.J., ADAMSON, N.J. AND BANN, K.L., 2013—Understanding the Late Triassic Mungaroo and Brigadier deltas of the Northern Carnarvon Basin, North West Shelf, Australia. In: Keep, M. and Moss, S.J. (eds), 2013, The Sedimentary Basins of Western Australia IV: Proceedings of the Petroleum Exploration Society of Australia Symposium, Perth, WA, 2013. 29 pp.

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BACKHOUSE, J., 2006—Triassic biostratigraphic study of the greater Exmouth Plateau, synthesis report. Geoscience Australia Petroleum Data Repository Destructive Analysis Report 1297, unpublished.

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BARBER, P., 2013—Oil exploration potential in the Greater Northern Australian – New Guinea Super Gas Province. In: Keep, M. and Moss, S.J. (eds), 2013, The Sedimentary Basins of Western Australia IV: Proceedings of the Petroleum Exploration Society of Australia Symposium, Perth, WA, 2013, 32 pp.

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DIREEN, N.G., STAGG, H.M.J., SYMONDS, P.A. AND COLWELL, J.B., 2008—Architecture of volcanic rifted margins: new insights from the Exmouth–Gascoyne margin, Western Australia. Australian Journal of Earth Sciences, 55, 341–363.

EDWARDS, D., BOREHAM, C.J., HOPE, J., PRESTON, J., LEPOIDEVIN, S., BUCKLER, T. AND HONG, Z., 2006—Molecular and isotopic composition of gas accumulations from the Exmouth Plateau and Exmouth Sub-basin, Carnarvon Basin. The APPEA Journal, 46(1), 669.

GONCHAROV, A., DEIGHTON, I., DUFFY, L., MCLAREN, S., TISCHER, M. AND HEINE, C., 2006—Basement and crustal controls on hydrocarbon maturation on the Exmouth Plateau, North West Australian Margin. Poster presentation at AAPG 2006 International Conference and Exhibition, Perth, Australia, November 5–8.

GRADSTEIN, F.M., OGG, J.G. SCHMITZ, M.D. AND OGG, G.M. (eds), 2012—The Geologic Time Scale 2012; Volumes 1 and 2. Elsevier BV, 1144 pp.

GRAIN, S.L., PEACE, W.M., HOOPER, E.C.D., MCCARTAIN, E., MASSARA, P.J., MARSHALL, N.G. AND LANG, S.C., 2013—Beyond the deltas: Late Triassic isolated carbonate build-ups on the Exmouth Plateau, Carnarvon Basin, Western Australia. In: Keep, M. and Moss, S.J. (eds), 2013, The Sedimentary Basins of Western Australia IV: Proceedings of the Petroleum Exploration Society of Australia Symposium, Perth, WA, 2013, 19 pp.

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JABLONSKI, D., PRESTON, J., WESTLAKE, S. AND GUMLEY, C.M., 2013—Unlocking the origin of hydrocarbons in the central part of the Rankin Trend, Northern Carnarvon Basin, Australia. In: Keep, M. and Moss, S.J. (eds), 2013, The Sedimentary Basins of Western Australia IV: Proceedings of the Petroleum Exploration Society of Australia Symposium, Perth, WA, 2013. 31 pp.

JAMES, A.T. AND BURNS, B.J., 1984—Microbial alteration of subsurface natural gas accumulations. The American Association of Petroleum Geologists Bulletin, 68(8), 957–960.

JENKINS, C.C., MAUGHAN, D.M., ACTON, J.H., DUCKETT, A., KORN, B.E. AND TEAKLE, R.P., 2003—The Jansz gas field, Carnarvon Basin, Australia. The APPEA Journal, 43(1), 303–324.

KAMINSKI, M.A., BAUMGARTNER, P.O., BOWN, P.R., HAIG, D.W., MCMINN, A., MORAN, M.J., MUTTERLOSE, J. AND OGG, J.G., 1992—Chapter 38. Magnetobiostratigraphic synthesis of Leg 123: sites 765 and 766 (Argo Abyssal Plain and Lower Exmouth Plateau). In: Gradstein, F.M., Adamson, A.C., Ludden, J.N. and Paog, C.W. (eds). Proceedings of the Ocean Drilling Program, Scientific Results, 123, 717–737.

KORN, B.E., TEAKLE, R.P., MAUGHAN, D.M. AND SIFFLEET, P.B., 2003—The Geryon, Orthrus, Maenad and Urania gas fields, Carnarvon Basin, Western Australia. The APPEA Journal, 43(1), 285–301.

KROH, F. AND WILLIAMSON, P.E., 2006—Preliminary AVO results from the Exmouth Plateau NW Australia. Preview, Australian Society of Exploration Geophysics, 122, 33–35.

LONGLEY, I.M., BUESSENSCHUETT, C., CLYDSDALE, L., CUBITT, C.J., DAVIS, R.C., JOHNSON, M.K., MARSHALL, N.M., MURRAY, A.P., SOMERVILLE, R., SPRY, T.B. AND THOMPSON, N.B., 2002—The North West Shelf of Australia – a Woodside perspective. In: Keep, M. and Moss, S.J. (eds), 2002, The Sedimentary Basins of Western Australia 3: Proceedings of the Petroleum Exploration Society of Australia Symposium, Perth, WA, 2002, 27–88.

MAFTEI, A., KING, E.J. AND FLORES, M.C., 2013—The Gorgon Field: an overview. In: Keep, M. and Moss, S.J. (eds), 2013, The Sedimentary Basins of Western Australia IV: Proceedings of the Petroleum Exploration Society of Australia Symposium, Perth, WA, 2013, 23 pp.

MARSHALL, N.G. AND LANG, S.C., 2013—A new sequence stratigraphic framework for the North West Shelf, Australia. In: Keep, M. and Moss, S.J. (eds), 2013, The Sedimentary Basins of Western Australia IV: Proceedings of the Petroleum Exploration Society of Australia Symposium, Perth, WA, 2013. 32 pp.

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PAYENBERG, T.H.D., HOWE, H., MARSH, T., SIXSMITH, P., KOWALIK, W.S., POWELL, A., RATCLIFFE, K., LASKY, V., ALLGOEWER, A., HOWE, R.W., MONTGOMERY, P., VONK, A. AND CROFT, M., 2013—An integrated regional Triassic stratigraphic framework for the Carnarvon Basin, NWS, Australia. In: Keep, M. and Moss, S.J. (eds), 2013, The Sedimentary Basins of Western Australia IV: Proceedings of the Petroleum Exploration Society of Australia Symposium, Perth, WA, 2013, 24 pp.

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SIBLEY, D., HERKENHOFF, F., CRIDDLE, D., AND MCLERIE, M. 1999—Reducing resource uncertainty using seismic amplitude analysis on the southern Rankin Trend, northwest Australia. The APPEA Journal, 39(1), 128–147.

SMALLWOOD, J.R., BANFIELD, J., COX, P., GRIFFIN, D., KUSUMANEGARA, Y., OWEN, P.B., PRESCOTTE, E., SANTONI, S. AND SMITH, J.G., 2010—Extending the Exmouth Plateau post-Callovian fairway: WA-390-P Phase I exploration. The APPEA Journal, 50. Extended Abstract.

SPENCER, L., SAYERS, J., BRADSHAW, J., BRADSHAW, M., FOSTER, C., MURRAY, A., EDWARDS, D., ZUCCARO, G., BUCHANAN, C. AND APPS, H., 1995—Australian Petroleum Systems Exmouth Plateau & Outer Rankin Platform Module. Australian Geological Survey Organisation Record 1995/80. 207 pp.

STAGG, H.M.J., COLWELL, J.B., 1994—The structural foundations of the Northern Carnarvon Basin. In: Purcell, P.G. and Purcell, R.R. (eds), The Sedimentary Basins of Western Australia. Proceedings of the Petroleum Exploration Society of Australia Symposium, Perth, WA, 349–372

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TINDALE, K., NEWELL, N., KEALL, J., AND SMITH, N., 1998—Structural evolution and charge history of the Exmouth Sub-basin, Northern Carnarvon Basin, Western Australia. In: Purcell, P.G. and R.R. (eds), 1998, The Sedimentary Basins of Western Australia 2: Proceedings of the Petroleum Exploration Society of Australia Symposium, Perth, WA, 1998. 447–472.

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Figures

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Figure 1

 Northern Carnarvon Basin-Exmouth Plateau-figure-1 map image
Structural elements of the Exmouth Plateau, showing petroleum fields and discoveries, the location of the regional seismic section shown in Figure 3 and the 2014 and 2015 Release Areas. Release Areas shown by outline only are discussed elsewhere.
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Figure 2

 Northern Carnarvon Basin-Exmouth Plateau-figure-2 map image
Stratigraphy and hydrocarbon discoveries of the Rankin Platform and Exmouth Plateau, based on the Northern Carnarvon Basin Biozonation and Stratigraphy Chart 36 (Kelman et al 2013). Geological Time Scale after Gradstein et al (2012).
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Figure 3

 Northern Carnarvon Basin-Exmouth Plateau-figure-3 map image
Seismic line 110r/09 across the Exmouth Plateau, Rankin Platform and Dampier Sub-basin. Interpretation by Geoscience Australia. Location of the seismic line is shown in Figure 1.
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Figure 4

 Northern Carnarvon Basin-Exmouth Plateau-figure-4 map image
Seismic and well data in the vicinity of the 2015 Release Areas on the Rankin Platform and Exmouth Plateau, Northern Carnarvon Basin. 2015 Release Areas shown by outline only are discussed elsewhere.
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