Total (60%) and Petronas (40%) are relinquishing WA-403-P two years early after a disappointing campaign in 2011 where the company completed the Laperouse-1 and Durville-1 wells that were based on the 2008 Malita 3D seismic survey, but fate was not kind.

Laperouse-1 in particular encountered hard rocks that slowed the drilling.

Instead, Total will focus on the 4070sq.km AC/P60, which sits across the prolific Vulcan Sub-basin and the northeastern Ashmore Platform.

The area, released as AC14-1, contains the Warb-1A and Pollard-1 oil shows, and is close to PTTEP's Cash-Maple and Oliver oil and gas fields. Cash-Maple is under development.

The Tenacious discovery is just outside the southern edge of the permit.

Water depths in the block are between 50-500m.

The area flanks a Jurassic depocentre with oil and gas-prone source rocks and there is good potential for structural and stratigraphic plays in Jurassic-Triassic, Cretaceous and Paleogene sandstones.

Pollard-1 was drilled by BHP Billiton in 1984 but was plugged and abandoned after only minor fluorescence was observed in basal Miocene cuttings.

No hydrocarbons were encountered within the Triassic section, however the interval as found to contain a thicker section of reservoir quality sandstone than had previously been drilled in the area.

There was also a lack of sealing Cretaceous claystone unit covering the Triassic and explorers downgraded the trap potential of similar structures on the Ashmore Platform.

Warb-1/1A was drilled 6km away by Western Mining Corporation in 1992.

Warb-1 was abandoned due to a mechanical failure and Warb-1A was re-spudded to test the Triassic and younger rocks.

WMC was looking for a prognosed basin margin fan, but it and the Plover Formation were absent at the location, and although residual oil was encountered in the Miocene carbonates of the Oliver Formation geochemical analysis indicated it was severely degraded and probably sourced from the Jurassic.

Despite that, the Miocene reservoir quality was good and there were indications of rocks that may be capable of sealing significant volumes in a favourable structural setting.

The other wells in the block were all dusters.

Sahul Shoal-1, drilled in the 1970s, confirmed the presence of porous and permeable lower Tertiary carbonates and proved the existence of possibly prospective Triassic sandstones with porosity and low permeability, while OMV's Cromwell-1A, the last well drilled in 2011, found some 200m of excellent quality Plover Formation reservoir but no seal.

Pokolbin-1, drilled by TCPL Resources in 1990, was also a duster with traces of hydrocarbons within the Lower Challis and Upper Pollard formations believed to have been sourced in situ.

Total is the latest company to secure a block from the 2014 acreage release, following on from Woodside Petroleum, which secured a block over the Londonderry High and Petrel Sub-basin in April, just off the Northern Territory coast.

From the 2015 acreage release both W15-9 and W15-13 were not offered, and AC15-2 also went without a bidder.

The areas have reverted to vacant acreage.