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Petrel Sub-basin

Release area W16-1, Petrel Sub-basin, Bonaparte Basin, Western Australia

Highlights

Bids close 8 December 2016

  • Proximal to the Blacktip gas field and the Marina gas accumulation
  • Proximal to the Blacktip and Ichthys pipelines
  • Shallow water depths of 30–70 m
  • Proven plays in anticlines, tilted fault blocks and structural/stratigraphic traps
  • Proven oil and gas petroleum systems
  • Special Notices apply, refer to Guidance Notes

Release Area W16-1 is located in the southwest part of the Petrel Sub-basin of the Bonaparte Basin, less than 10 km offshore and approximately 300 km from Darwin in water depths of up to 70 m (Figure 1). The Release Area comprises 57 full and 13 part graticular blocks (5 230 km2) and is adjacent to the Blacktip gas field, as well as the Marina gas accumulation. Gas production from the Blacktip field commenced in 2009 via the Blacktip pipeline. The Release Area also contains the Berkley 1 and Lesueur 1 wells.

The Petrel Sub-basin is an asymmetric, northwest-trending Paleozoic rift in the eastern Bonaparte Basin. The sub-basin contains a thick Paleozoic succession overlain by thinner Mesozoic sediments (Figure 2 and Figure 3). Sedimentation in the sub-basin commenced in the Cambrian. A northwest-trending rift was initiated in the Late Devonian to Mississippian being filled by a thick succession of marine to fluvio-deltaic sediments. 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. in 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 numerous gas accumulations, including the producing Blacktip gas field, as well as the Turtle oil and gas accumulation and the Barnett oil accumulation. Permian marginal marine, fluvial and glacial reservoirs within the Kulshill Group are proven hydrocarbon reservoirs in the Blacktip structure. 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 (Figure 2 and Figure 3). This includes source rocks within the Bonaparte Formation (Langfield Group equivalent) and the Tanmurra Formation (Weaber Group). Sufficient deep drilling has not been undertaken in the western Petrel Sub-basin to fully evaluate the western extent of the petroleum system, although Marina 1 and Lesueur 1 both had gas and oil shows in the Carboniferous–lower Permian succession and are within the Release Area (Figure 2, Figure 3 and Figure 4). The identification of the Beehive Prospect to the east of the Release Area in Carboniferous and Ordovician rocks, raises the possibility of unevaluated older plays. The Release Area offers a range of play types including horst blocks and rotated fault blocks, as well as inversion-related anticlines, fault dependent closures, fault rollover anticlines and stratigraphic traps (Figure 4).

Figure 5 shows data coverage in the region. 3D seismic coverage is minimal, with some of the Blacktip 3D grid overlapping the corner of the Release Area. 2D seismic coverage is dense on the eastern edge of the Release Area but minimal further westward (Figure 5).





Figures

Figure 1

Structural elements of the Petrel Sub-basin in the vicinity of the 2016 Release Area (after Colwell and Kennard, 1996), showing petroleum fields, key wells, and the 2016 Release Area


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Figure 2

Upper Paleozoic and Mesozoic stratigraphy and hydrocarbon shows in the Petrel Sub-basin based on the Bonaparte Basin Biozonation and Stratigraphy Chart (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

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

Play types in the vicinity of the Release Area in the Petrel Sub-basin, Bonaparte Basin


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Figure 5

Seismic and well data in the vicinity of the Release Area in the Petrel Sub-basin, Bonaparte Basin


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