New Exploration Opportunities in the Offshore Northern Perth Basin

Release Area W11-18 is a very large block over the offshore northern Perth Basin, covering parts of the Abrolhos, Houtman and Vlaming sub-basins and the Beagle and Turtle Dove ridges. Geoscience Australia (GA) has assessed the petroleum prospectivity of this area as part of the Australian Government's Offshore Energy Security Program. This assessment includes the first published synthesis of data from fourteen new field wildcat wells drilled in this part of the basin since the Cliff Head-1 discovery (2001), and the interpretation of new regional 2D seismic data acquired during GA survey 310 (2008-2009). A refined tectono-stratigraphic model for the offshore basin provides insights into basin evolution and prospectivity.

Oil has been produced since 2006 from the Cliff Head oil field in WA-31-L, which is directly adjacent to Release Area W11-18. Three petroleum discoveries are included within the Release Area, with oil and gas in Dunsborough-1, and gas in Frankland-1 and Perseverance-1. These accumulations are reservoired in Permian sandstones and have primarily been sourced from the Hovea Member of the Kockatea Shale, which has also sourced the majority of producing oil and gas fields of the onshore Perth Basin.

New seismic data show Permo-Triassic strata that are stratigraphic equivalents of the productive onshore and nearshore Perth Basin petroleum system, also occur within Permian half-graben in the outer Abrolhos and Houtman sub-basins. Source rock, oil stain and fluid inclusion sampling from this interval suggest that the proven onshore-nearshore petroleum system is also effective and widespread in the offshore. There is also evidence for an active Jurassic petroleum system within the Release Area. The Release Area offers a range of plays in a variety of water depths, predominantly less than 200 m, and is highly prospective for oil and gas.

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