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Central Caswell Sub-basin

Bids close 21 April 2016

  • Adjacent to the Ichthys and Prelude/Concerto gas developments
  • Proximal to Burnside, Crown/Proteus and Lasseter gas accumulations
  • Release Area W15-4 includes the Caswell oil accumulation and Marabou gas discovery
  • Close to Ichthys Gas Pipeline to Bladin Point, Darwin (currently under construction)
  • Shallow to deep water depths, 100–450 m
  • Quality reservoirs and seals, multiple potential oil- and gas-prone source rocks and active petroleum systems
  • Special Notices apply, refer to Guidance Notes

Release Areas W15-3 and W15-4 are located within the central Caswell Sub-basin, southwest of the Ichthys, Prelude and Concerto gas accumulations (Figure 1). Release Area W15-3 consists of six graticular blocks, approximately 25 km east of the Burnside gas accumulation, in shallow water depths (100–130 m). Release Area W15-4 is a larger area consisting of 34 graticular blocks, in water depths of 100 to 450 m. It is adjacent to the Burnside gas accumulation and incorporates the Caswell oil accumulation and Marabou gas discovery. The Release Areas lie between 160 to 300 km from the northwest coast of Western Australia where multiple construction activities are in progress. These include Prelude FLNG, the Ichthys LNG Project and gas pipeline and Browse FLNG.

Numerous petroleum systems have been proven within the Caswell Sub-basin. Organic-rich rocks with fair to moderate oil potential occur within the Plover, Vulcan and Echuca Shoals formations. Gas-prone, high-quality coals and pro-delta shales occur within the Plover Formation (Figure 2). Proven combined structural and stratigraphic plays include Jurassic horsts/tilted fault blocks and associated drape anticlines (Figure 3), and Cretaceous submarine canyon fill and basin floor fans. Figure 4 shows the existing data coverage of the region, with few wells and numerous 3D seismic surveys throughout Release Area W15-4, whereas Release Area W15-3 only has 2D seismic data.

Petroleum systems elements

Caswell Sub-basin

Sources
  • Lower–Middle Jurassic fluvio-deltaic Plover Formation (oil- and gas-prone)
  • Callovian–Valanginian marine Vulcan and Montara formations (oil-prone)
  • Valanginian–Aptian marine Echuca Shoals Formation (oil-prone)
Reservoirs
  • Lower Triassic marine Kinmore Group-equivalents
  • Lower–Middle Jurassic fluvio-deltaic Plover Formation
  • Middle–Upper Jurassic marine Montara (Ichthys) Formation
  • Upper Jurassic–Lower Cretaceous marine upper Vulcan Formation (Brewster Member)
  • Lower Cretaceous Echuca Shoals Formation, lower and upper Jamieson Formation (shallow marine sandstones, submarine fans and ‘ponded’ turbidites)
  • Upper Cretaceous marine Fenelon and Puffin formations
Seals Regional Seals
  • Upper Jurassic–Lower Cretaceous marine Vulcan Formation
  • Lower Cretaceous marine Echuca Shoals and Jamieson formations (claystone seal 500–600 m thick across the sub-basin)

Intraformational Seals

  • Lower–Middle Jurassic fluvio-deltaic Plover Formation
  • Upper Cretaceous marine Puffin Formation
Traps
  • Jurassic horsts/tilted fault blocks and associated drapes
  • Cretaceous submarine canyon fill, basin floor fans and ‘ponded’ turbidite stratigraphic traps

Infrastructure and markets

There are four gas developments at various stages of implementation in the Browse Basin, including a gas pipeline to Bladin Point, Darwin and two FLNG vessels. The Ichthys gas pipeline is currently under construction and will come within 50 km of the Release Areas. First gas from the Ichthys accumulation is planned to come online by 2017. Prelude FLNG, servicing the Prelude and Concerto accumulations, is expected to produce LNG in 2016 and Browse FLNG is planned to commercialise the Torosa, Brecknock and Calliance gas accumulations with an FID targeted for late 2015.

Critical risks

Proven petroleum systems and migration pathways have been established within Release Area W15-4. Poor reservoir development and low porosities were found in the oil-bearing Campanian sediments of the Caswell 1 and 2 wells; though fair to excellent reservoir characteristics were exhibited in the same unit of the nearby Walkley 1 well, which is water-wet. Reservoir and charge were proven at Marabou 1 with good quality Campanian gas-bearing sandstones. However, the poor quality stratigraphic seal led to this well being plugged and abandoned. Continued success in the region thus relies on the identification of additional valid well sealed traps in areas of good reservoir quality, with access to charge from effective source rocks.

Data sets

Wells Data and Seismic Survey listings for the central Caswell Sub-basin are available on the Supporting Information page.

Geoscience Australia products

Regional geology and seismic

Stratigraphy

Petroleum systems and accumulations

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Contact Geoscience Australia’s Sales Centre for more information: phone +61 (0)2 6249 9966, email sales@ga.gov.au

AGSO, 2001—Line drawings of AGSO – Geoscience Australia’s Regional Seismic Profiles, Offshore Northern and Northwestern Australia. Australian Geological Survey Organisation Record, 2001/36, 174pp.

AGSO BROWSE BASIN PROJECT TEAM, 1997—Browse Basin High Resolution Study, Interpretation Report, North West Shelf, Australia. Australian Geological Survey Organisation Record 1997/38.

BAN, S. AND PITT, G., 2006—The Ichthys giant gas-condensate field. 2006 AAPG International Conference and Exhibition, 5–8 November, Perth, Australia, Abstract.

BENSON, J.M., BREALEY, S.J., LUXTON, C.W., WALSHE, P.F. AND TUPPER, N.P., 2004—Late Cretaceous ponded turbidite systems: a new stratigraphic play fairway in the Browse Basin. The APPEA Journal, 44(1), 269–285.

BLEVIN, J.E., BOREHAM, C.J., SUMMONS, R.E., STRUCKMEYER, H.I.M. AND LOUTIT, T.S., 1998—An effective Lower Cretaceous petroleum system on the North West Shelf: evidence from the Browse Basin. 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, 397–420.

BLEVIN, J.E., STRUCKMEYER, H.I.M., CATHRO, D.L., TOTTERDELL, J.M., BOREHAM, C.J., ROMINE, K.K., LOUTIT, T.S. AND SAYERS, J., 1998—Tectonostratigraphic framework and petroleum systems of the Browse Basin, North West Shelf. 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, 369–395.

BRINCAT, M.P., LISK, M., KENNARD, J.M., BAILEY, W.R. AND EADINGTON, P.J., 2004—Evaluating the oil potential of the Caswell Sub-basin; insights from fluid inclusion studies. Special Publication - Northern Territory Geological Survey, 437–455.

FUJIMOTO, M., YOSHIDA, T. AND LONG, A., 2010—Improved seismic inversion and reservoir description of the Ichthys gas-condensate field, Browse Basin, Western Australia. The APPEA Journal, 50(1) Presentation.

KELMAN, A.P., KENNARD, J.M., NICOLL, R.S., LAURIE, J.R., EDWARDS, D.S., KHIDER, K. AND LE POIDEVIN, S., 2014—Browse Basin Biozonation and Stratigraphy 2014 Chart 32. Geoscience Australia Biozonation and Stratigraphy Chart Series (http://www.ga.gov.au/corporate_data/76687/Chart_32_Browse_Basin_2014.pdf).

KENNARD, J.M., DEIGHTON, I., RYAN, D., EDWARDS, D.S. AND BOREHAM, C.J., 2004—Subsidence and thermal history modelling: new insights into hydrocarbon expulsion from multiple petroleum systems in the Browse Basin. In: Ellis, G.K., Baillie, P.W. and Munson, T.J. (eds), Timor Sea Petroleum Geoscience. Proceedings of the Timor Sea Symposium, Darwin, 19–20 June 2003. Northern Territory Geological Survey, Special Publication 1, 411–435.

LAWRENCE, S.H.F., THOMPSON, M., RANKIN, A.P.C., ALEXANDER, J.C., BISHOP, D.J. AND BOTERHOVEN, B., 2014—A new structural analysis of the Browse Basin, Australian North West Margin. The APPEA Journal 54, 1–10.

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.

RADLINSKI, A.P., KENNARD, J.M., EDWARDS, D.S., HINDE, A.L. AND DAVENPORT, R., 2004—Hydrocarbon generation and expulsion from Early Cretaceous source rocks in the Browse Basin, North West Shelf, Australia: a small angle neutron scattering study. The APPEA Journal, 44(1), 151–180.

STRUCKMEYER, H.I.M., BLEVIN, J.E., SAYERS, J., TOTTERDELL, J.M., BAXTER, K. AND CATHRO, D.L., 1998—Structural evolution of the Browse Basin, North West Shelf: new concepts from deep-seismic data. 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, 345–367.

SYMONDS, P.A., COLLINS, C.D.N. AND BRADSHAW, J., 1994—Deep structure of the Browse Basin: implications for basin development and petroleum exploration. In: Purcell, P.G. and R.R. (eds), The Sedimentary Basins of Western Australia: Proceedings of Petroleum Exploration Society of Australia Symposium, Perth, 1994, 315–331.

VOLK, H., BRINCAT, M.P., GEORGE, S.C., KENNARD, J. M., EDWARDS, D.S., BOREHAM, C.J., AHMED, M. AND LISK, M. 2005—Clues to fill histories of gas fields in the Caswell Sub-basin; evidence from the distribution and geochemistry of palaeo-oils. The APPEA Journal, 45(1), 679.

WILLIS, I., 1988—Results of exploration, Browse Basin, North West Shelf, Western Australia. In: Purcell, P.G. and R.R. (eds), The North West Shelf, Australia: Proceedings of Petroleum Exploration Society of Australia Symposium, Perth, 1988, 259–272.

Figures

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Figure 1

 Browse Basin-Central Caswell Sub-basin-figure-1 map image
Structural elements of the Caswell Sub-basin in the vicinity of the 2015 Release Areas, showing petroleum fields and discoveries, the location of the regional seismic section (Figure 3), and the 2015 and 2014 Release Areas.
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Figure 2

 Browse Basin-Central Caswell Sub-basin-figure-2 map image
Stratigraphy and hydrocarbon discoveries in the Caswell Sub-basin and Brecknock-Scott Reef Trend based on the Browse Basin Biozonation and Stratigraphy Chart 32 (Kelman et al, 2014). Geologic Time Scale after Gradstein et al (2012).
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Figure 3

 Browse Basin-Central Caswell Sub-basin-figure-3 map image
Seismic line BBHR07 across the Caswell Sub-basin. Interpretation by Geoscience Australia. Location of the seismic line is shown in Figure 1.
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Figure 4

 Browse Basin-Central Caswell Sub-basin-figure-4 map image
Seismic and well data in the vicinity of the 2015 Release Areas in the Central Caswell Sub-basin, Browse Basin.
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