Dampier Sub-basin

Release Areas W17-5 and W17-6, offshore Western Australia

Highlights

Bids close for release area W17-5 on Thursday 19 October 2017.

Prequalification for release area W17-6 closes on Thursday 5 October 2017, with the cash bidding auction to be held on 8 February 2018.

  • Within one of Australia’s premier offshore producing basins
  • Release Area W17-5 lies on trend between the Legendre and Talisman oil accumulations, while Cash Bid Release Area W17-6 overlies the Gungurru oil and gas accumulation
  • Shallow water (40–80 m)
  • Oil-prone Upper Jurassic and gas-prone Triassic to Middle Jurassic source rocks
  • Stacked structural and stratigraphic targets at Triassic, Jurassic and Lower Cretaceous levels
  • Overlying, and proximal to gas pipelines
  • Further guidance available, refer to 2017 Special Notices

Release Areas W17-5 and W17-6 are small areas comprising 4 and 2 graticular blocks, respectively, lying along the eastern flank of the Dampier Sub-basin. These areas are considered mature in exploration terms, and Release Area W17-6 is available for cash bidding. Release Area W17-5 overlies a northeasterly structural trend (‘Legendre Trend’) which hosts the Legendre oil field just to its south and the Talisman and Amulet oil fields just to its northeast, as well as the Ajax 1 oil discovery and Forestier 1 gas discovery (Figure 1). Further to the southwest, Release Area W17-6 hosts the Gungurru oil and gas field, on the heavily faulted eastern flank of the Lewis Trough, with producing fields Wandoo and Reindeer just to the south and west, respectively (Figure 1).

The Dampier Sub-basin is one of a series of large rift depocentres of the Northern Carnarvon Basin. The sub-basin is an elongate northeast-trending depocentre 170 km in length and 100 km in width, and contains Paleozoic to Cenozoic sedimentary successions 10–20 km in thickness. The main structural elements of the Dampier Sub-basin are aligned northeast–southwest, which from northwest to southeast are: the Kendrew Trough, Madeleine Trend, Lewis Trough, Legendre Trend and Enderby Terrace (Figure 3).

The Dampier Sub-basin hosts proven petroleum systems. Triassic, Lower–Middle and Upper Jurassic source rocks have expelled hydrocarbons that are reservoired in both structural and stratigraphic traps. Gas is predominantly sourced from Triassic to Middle Jurassic fluvio-deltaic sediments of the Mungaroo and Brigadier formations, the Murat Siltstone, and the Athol and Legendre formations, while oil is predominantly sourced from the Upper Jurassic Dingo Claystone (Figure 2). Structural trap styles in the sub-basin include tilted fault blocks, fault dependent rollovers, anticlines, drape features and horsts, while stratigraphic trap styles are predominantly of Upper Jurassic basin-floor fan systems and Lower Cretaceous marginal marine transgressive sands (Figure 3).

Figure 4 shows the data coverage for the Dampier Sub-basin in the vicinity of the Release Areas, highlighting well concentrations and a high density of 2D seismic lines. In Release Area W17-5, Ajax 1/ST 1 and Forestier 1/ST 1 are oil and gas discoveries, respectively. Several other dry wells within the Area (Charm 1, Legendre 2, Nelson Rocks 1 and Polaris 1) provide stratigraphic information while the Release Area is completely covered by 3D seismic surveys Panaeus 1999 MC3D MSS, Panaeus 2 North MSS and Panaeus MC3D MSS. In Release Area W17-6, apart from the Gungurru oil and gas field, Cherring 1 is a gas discovery with an oil show and Coojong 1 has an oil show. Well Nickol Bay 1 provides further stratigraphic information in the sparsely explored east, while the Release Area is completely covered by 3D seismic surveys Panaeus MC3D MSS and Panaeus East 2001 MC3D MSS.