Pilot secured the block from US independent Murphy Oil.

Murphy drilled three wells in the permit with Kuwait's state oiler Kufpec and Korea's Samsung Oil & Gas but Munia-1, Koel-1 and Cisticola-1 failed to find the 100 million barrel plus targets it was looking for in the $120 million plus campaign.

Its partners have walked already from the costly block, and with Murphy cutting back its exploration efforts around the world, Pilot has been willing to walk in and carry out the low-cost year four work program.

Pilot will be assigned the interest in return for paying Murphy a net profit interest on any future hydrocarbon production from within the permit.

Pilot will formally take ownership of WA-481-P when its primary term expires on August 19 and will meet the $300,000 spending commitment on geological and geophysical studies.

The discretionary years five and six require two exploration wells, with sources telling Energy News that the focus on exploration is likely to be in the inboard areas.

Drilling in the permit could also be much cheaper than expected, and closer to onshore drilling costs.

For Pilot, and any other explorers looking in the offshore Perth Basin, the great white whale is finding a repetition of Cliff Head. Significant amounts of oil and gas have been generated, but the trick remains finding a valid trap.

The major exploration risks in the area are effective seals, trap breach and preservation of palaeo-accumulations.

The degree of faulting generally increases outboard from the Abrolhos Sub-basin to Houtman Sub-basin, but increased risk associated with this trend may be partially offset by a concurrent outboard increase in thickness of regional and intraformational seals.

High CO2 content is also a localised risk for the north-eastern part of the block.

For Pilot, WA-481-P is a low-cost option over a promising block surrounding the only offshore facilities in the basin.

The explorer will be focusing on targets in the Dongara Sandstone and the Irwin River Coal Measures.

Both oil and gas are proven within the permit, with the non-commercial Frankland gas and the Dunsborough oil discoveries representing possible contingent resources for future development.

WA-481-P is west of the onshore Dongara, Beharra Springs and Waitsia gas fields, and the Jingemia, Hovea and Cliff Head oil fields, while EP 437 is about 10km to the east.

Murphy was awarded WA-481-P in 2012 and promised a guaranteed work program of 4738km of 2D seismic reprocessing, 550km of new 2D and 2550sq.km of new 3D seismic and the three wells in 2015.

The area, which covers much of WA-286-P, the original Cliff Head licence, had been abandoned by explorers in 2009 earlier after exploration failed to find any follow-ups to the original Cliff Head-1 discovery.

The block takes in the Abrolhos Sub-Basin with some parts of the Houtman and northern Vlaming sub-basins, and has water depths typically less than 200m.

A 2010 Geoscience Australia study over the area highlighted more regionally extensive source rocks are offshore than previously thought, where they have good to excellent potential for generating oil.

There are nine well penetrations resulting in three small discoveries within WA-481-P, and there is a mix of 2D and 3D seismic, shot between the 1960s and 2009.

The first offshore Perth Basin well, Gun Island-1 was drilled in 1968. Exploration ceased in 1983 and drilling rigs did not return for almost 20 years.

Other discoveries in the basin include oil shows in Gage Roads-1, Araucaria-1 and a non-commercial gas at Marri-1 in the Vlaming Sub-basin and oil and gas in the Houtman-1 in the Houtman Sub-basin.

When Cliff Head-1 was drilled in 2001 it led to the uptake of permits but it was not until 2007 that there was any level of follow-up success with Frankland-1, Dunsborough-1 and Perseverance-1 all finding gas.

Drilling of wells such as Vindara-1 and Mentelle-1 helped confirm the potential for oil below the regional Kockatea shale seal, but most wells in the offshore Perth Basin have been dry.

Perseverance-1 contained 40% carbon dioxide, while appraisal drilling in 2009 downgraded Frankland and proved residual oil in Dunsborough.

Lilac-1 was the last offshore exploration well and encountered sands with weak gas shows.

Assignment of the permit interest to Pilot is conditional on regulatory approval.

The opportunity was originally identified in collaboration with Pilot's joint venture partner in the onshore EP 437 permit, Key Petroleum.

Under a co-operation agreement Key has an option to secure a 40% interest on the same terms as Pilot.

Murphy remains active in Australia and maintains AC/P57, AC/P58 and AC/P59 (all 60%), EPP 43 in the Great Australian Bight (50%), 20% in WA-408-P in the Browse Basin, and 100% of WA-476-P in the Carnarvon Basin.