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Petrel Sub-basin

NT15-1: bids close 29 October 2015
NT15-2 and W15-1: cash bids close 15 October 2015 (pre-qualification), 4 February 2016 (auction)

  • Release Areas W15-1 and NT15-2 contain the Turtle oil and gas and Barnett oil accumulations respectively
  • Proximal to the offshore Blacktip gas field, and Petrel, Tern and Frigate gas accumulations, and the onshore Waggon Creek, Weaber, Garimala and Keep River gas accumulations
  • Proximal to the Blacktip pipeline and Ichthys pipeline (under construction)
  • Shallow water depths, ~50–100 m
  • Proven plays in anticlines, tilted fault blocks and structural/stratigraphic traps
  • Multiple potential oil- and gas-prone source rocks and active petroleum systems
  • Special Notices apply, refer to Guidance Notes

Release Areas NT15-1, NT15-2 and W15-1 are located in the Petrel Sub-basin of the Bonaparte Basin. Release Area NT15-1 is located in the centre of the sub-basin, approximately 100 km offshore and 180 km from Darwin (Figure 1). Release Areas NT15-2 and W15-1 are in the southern Petrel Sub-basin, less than 20 km offshore and approximately 275 km from Darwin. Release Areas NT15-2 and W15-1 contain known accumulations and are available for cash bidding. Release Area NT15-2 (3 full and 11 part graticular blocks) contains the Barnett oil accumulation, and Release Area W15-1 (3 full and 5 part graticular blocks) contains the Turtle oil and gas accumulation. Barnett 1, 2 and 3 have been drilled within Release Area NT15-2, and Cape Ford 1, Turtle 1 and Turtle 2 have been drilled within Release Area W15-1.

Release Area NT15-1 is large (47 full and 4 part graticular blocks), adjacent to the Petrel gas accumulation and within 100 km of the Blacktip gas field and the Tern, Frigate and Penguin gas accumulations. No wells have been drilled within this Release Area. Gas production from the Blacktip field commenced in 2009 via the Blacktip pipeline.

The Petrel Sub-basin is an asymmetric, northwest-trending Paleozoic rift in the eastern Bonaparte Basin. The sub-basin contains a thick Paleozoic section overlain by thinner Mesozoic sediments (Figure 2, Figure 3). Sedimentation in the sub‑basin commenced in the Cambrian and a northwest-trending rift was initiated in the Late Devonian to Mississippian. Structurally, the Petrel Sub-basin comprises a broad northwest-trending syncline that plunges to the northwest, resulting in exposure of lower Paleozoic sediments in the southern onshore area (e.g. Bonaparte 1 and Ningbing 1), and in the progressive sub-cropping of upper Paleozoic, Mesozoic and Cenozoic sediments offshore. The Petrel Sub-basin is a proven Paleozoic hydrocarbon province containing the producing Blacktip gas field, numerous gas accumulations and the Turtle oil and gas and Barnett oil accumulations. Permian marginal marine, fluvial and glacial reservoirs within the Kulshill Group are proven hydrocarbon reservoirs. Structural traps containing Devonian to Triassic reservoirs are sealed by Carboniferous to Jurassic shales and carbonates.

Oil and gas in Permo–Carboniferous reservoirs in the southern Petrel Sub-basin are sourced from a lower Carboniferous petroleum system as seen in the Turtle and Barnett accumulations within Release Areas NT15-2 and W15-1 (Figure 2, Figure 3). This includes source rocks from the Bonaparte Formation (Langfield Group equivalent) and the Tanmurra Formation (Weaber Group). The identification of the Beehive Prospect in Carboniferous and Ordovician rocks, raises the possibility of unevaluated older plays in Release Areas NT15-2 and W15-1. Release Area NT15-1 lies within the proven Permian petroleum system that has charged numerous nearby gas accumulations, including the Petrel, Tern and Frigate accumulations (Figure 2, Figure 3, Figure 4 and Figure 5). The Release Areas include a range of trap styles such as horst blocks, rotated fault blocks, inversion- and salt-related anticlines and stratigraphic traps. Infrastructure in the region is expanding, including the continuing construction of the Ichthys pipeline, which could facilitate the development of any new discoveries in the sub-basin. 3D seismic coverage over the three Release Areas in the Petrel Sub-basin is minimal, although 2D coverage is better, particularly over Release Areas NT15‑2 and W15-1 (Figure 6).

Petroleum systems elements

Petrel Sub-basin



Sources
  • Permian pro-delta, shoreface and open marine Hyland Bay Subgroup
  • Permian fluvial shales and coaly shales of the Keyling Formation
  • Lower Carboniferous Bonaparte Formation equivalent (Langfield Group equivalent)
  • Lower Carboniferous Milligans Formation, Kingfisher Shale and Tanmurra Formation
  • Upper Devonian–Carboniferous Bonaparte Formation
  • Other as yet unproven Ordovician sources
Reservoirs
  • Lower Triassic marginal marine Ascalon Formation and Permian lacustrine Penguin Formation (Mount Goodwin Subgroup)
  • Permian shoreface to marine Tern, Cape Hay and Torrens formations (Hyland Bay Subgroup)
  • Permian marginal marine Keyling, fluvial Quoin, and glacial Treachery and Kuriyippi formations
  • Carboniferous marine Aquitaine and Arco formations
  • Devonian–Carboniferous marine Tanmurra (reefal), Milligans (basin floor fans) and Bonaparte formations
  • Other as yet untested Ordovician sediments
Seals Regional seals
  • Jurassic–Cretaceous marine shales of the Flamingo and Bathurst Island groups
  • Triassic marine shales of the Mount Goodwin Subgroup
  • Permian marine Fossil Head Formation
  • Carboniferous Kingfisher Shale, Milligans and Bonaparte formations

Intraformational seals

  • Permian shoreface to open marine carbonates of the Dombey and Pearce formations (Hyland Bay Subgroup)
  • Carboniferous marine Weaber Group and Langfield Group equivalent
  • Devonian marine Ningbing Group equivalent
  • Ordovician–Silurian salt diapirs
Traps
  • Salt diapirs, rollover/inversion anticlines, salt-induced anticlines, tilted fault blocks, drape and stratigraphic pinch-outs, reefs, pinnacle reefs, carbonate mounds

Infrastructure

Release Areas NT15-1, NT15-2 and W15-1 are in close proximity to the Blacktip gas pipeline and the under construction Ichthys gas pipeline. The three Release Areas are close to the offshore Blacktip gas field and the Petrel, Tern and Frigate gas accumulations, the Turtle oil and gas accumulation and the Barnett oil accumulation. Release Areas NT15-2 and W15-1 are also within 70 km of the onshore Waggon Creek, Weaber, Garimala and Keep River gas accumulations.

Critical risks

Exploration success in the region is dependent on the identification of good quality reservoirs and traps capable of holding economic volumes of hydrocarbons that have access to active source kitchens. Exploration risks include preservation of hydrocarbon accumulations following Early and Late Carboniferous tectonic activity, Triassic uplift and erosion, and Miocene fault reactivation. Salt diapir intrusions, as seen at Pelican Island 1, Matilda 1 and Sandpiper 1, may locally disturb stratigraphy and primary seal capacity, though may provide secondary sealing capability. As oil shows occur throughout the Carboniferous and Permian sediments in wells in the southern Petrel Sub‑basin, further investigation of vertical and lateral seal integrity is required. Reservoir and source rock quality is variable and poorly understood in older units, with the preservation of porosity and permeability within Devonian–Carboniferous reservoirs and the Keyling Formation a significant risk. To date, no wells have penetrated Silurian or older Paleozoic units in the offshore Bonaparte Basin, thus offshore plays of this age are highly speculative. Biodegradation and fresh-water flushing is a risk in shallow reservoirs as demonstrated in the Turtle and Barnett accumulations, although oil in deeper reservoirs may be unaltered. Elevated geothermal gradients during the Middle Jurassic as modelled in Keep River 1 may affect the timing of hydrocarbon generation and expulsion in the southern Petrel Sub-basin, and adversely affect reservoir quality.

Data sets

Wells Data and Seismic Survey listings for the Petrel Sub-basin are available in the Supporting Information section.

Geoscience Australia products

Regional geology and seismic

Stratigraphy

Petroleum systems and accumulations

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BANN, K.L., KLOSS, O., WOOD, G.R., LANG, S.C., KASSAN, J. AND BENSON, J., 2004—Palaeo-environments and depositional history of the Tern Field, Bonaparte Basin. In: Ellis, G.K., Baillie, P.W. and Munson, T.J. (eds), Timor Sea Petroleum Geoscience: Proceedings of the Timor Sea Symposium, Darwin, Northern Territory, 19–20 June 2003, Northern Territory Geological Survey Special Publication 1, 521–538.

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EDWARDS, D.S., KENNARD, J.M., PRESTON, J.C., SUMMONS, R.E., BOREHAM, C.J. AND ZUMBERGE, J.E., 2000—Bonaparte Basin; geochemical characteristics of hydrocarbon families and petroleum systems. AGSO Research Newsletter, December, 14–19.

GIBSON-POOLE, C.M., LANG, S.C., STREIT, J.E., KRAISHAN, G.M. AND HILLIS, R.R., 2002—Assessing a basin's potential for geological sequestration of carbon dioxide; an example from the Mesozoic of the Petrel Sub-basin, NW Australia. 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, 439–463.

GONCHAROV, A.G., COLLINS, C.D.N., PETKOVIC, P. AND FOMIN, T.N., 1999—Seismic velocities in the Petrel Sub-basin from the ocean-bottom seismograph studies: implications for crustal structure and petroleum prospecting. The APPEA Journal, 39(1), 729–730.

GORTER, J.D., 2006—Fluvial deposits of the Lower Kulshill Group (Late Carboniferous) of the southeastern Bonaparte Basin, Western Australia. 2006 AAPG International Conference and Exhibition, 5–8 November, Perth, Australia, Abstract.

GORTER, J.D., JONES, P.J., NICOLL, R.S. AND GOLDING, C.J., 2005—A reappraisal of the Carboniferous stratigraphy and the petroleum potential of the southeastern Bonaparte Basin (Petrel Sub-basin), northwestern Australia. The APPEA Journal, 45(1), 275–295.

GORTER, J.D., AND MCKIRDY, D.M., 2013—Early Carboniferous Petroleum Source Rocks of the Southeastern Bonaparte 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.

GORTER, J.D., NICOLL, R.S., CAUDULLO, A., PURCELL, R.R. AND KOSTAS, K., 2010—Latest Permian (Changhsingian) to Early Triassic (Induan-Olenekian) biostratigraphy, depositional environment, reservoir and source rock potential of the Mt Goodwin Sub-group at Blacktip gas field, southeastern Bonaparte Basin, Australia. The APPEA Journal 50(1), 203–240.

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GORTER, J.D., REXILIUS, J.P., POWELL, S.L. AND BAYFORD, S.W., 2002—Late early to mid-Miocene patch reefs, Ashmore Platform, Timor Sea; evidence from 2D and 3D seismic surveys and petroleum exploration wells. 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, 355–376.

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KENNARD, J.M., DEIGHTON, I., EDWARDS, D.S., BOREHAM, C.J. AND BARRETT, A.G., 2002—Subsidence and thermal history modelling: new insights into hydrocarbon expulsion from multiple petroleum systems in the Petrel Sub-basin, Bonaparte Basin. 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, 409–437.

KLOSS, O., WOOD, G.R., BENSON, J., LANG, S.C., BANN, K.L. AND KASSAN, J., 2004—A revised depositional model for the Cape Hay Formation, Petrel Field, northern Australia. In: Ellis, G.K., Baillie, P.W. and Munson, T.J. (eds), Timor Sea Petroleum Geoscience: Proceedings of the Timor Sea Symposium, Darwin, Northern Territory, 19–20 June 2003, Northern Territory Geological Survey, Special Publication, 1, 503–518.

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Figures

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Figure 1

 Bonaparte Basin-Petrel Sub-basin-figure-1 map image
Structural elements of the Petrel Sub-basin (after Colwell and Kennard, 1996) showing petroleum fields and discoveries, the location of the 2014 and 2015 Release Areas and seismic lines (Figure 4 and Figure 5)
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Figure 2

 Bonaparte Basin-Petrel Sub-basin-figure-2 map image
Upper Paleozoic and Mesozoic stratigraphy and hydrocarbon discoveries of the Petrel Sub-basin and Londonderry High based on the Bonaparte Basin Biozonation and Stratigraphy Chart 34 (Kelman et al, 2014). Geologic Time Scale after Gradstein et al (2012), basin phases after Colwell and Kennard (1996)
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Figure 3

 Bonaparte Basin-Petrel Sub-basin-figure-3 map image
Paleozoic stratigraphy and hydrocarbon discoveries of the Petrel Sub-basin based on the Bonaparte Basin Biozonation and Stratigraphy Chart 34 (Kelman et al, 2014). Geologic Time Scale after Gradstein et al (2012), basin phases after Colwell and Kennard (1996)
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Figure 4

 Bonaparte Basin-Petrel Sub-basin-figure-4 map image
Seismic Line r9710006 across the southern Petrel Sub-basin. Interpretation after (Kennard et al, 2002). Location of seismic line is shown on Figure 1
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Figure 5

 Bonaparte Basin-Petrel Sub-basin-figure-5 map image
Seismic Line r9710003 across the Petrel Sub-basin. Interpretation after (Kennard et al, 2002). Location of seismic line is shown on Figure 1
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Figure 6

 Bonaparte Basin-Petrel Sub-basin-figure-6 map image
Seismic and well data in the vicinity of the Release Areas in the Petrel Sub-basin, Bonaparte Basin
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