Drilled by the Premium Wilcraft rig to a total depth of 1755m, Dunsborough-1 was the third and final well to be drilled in an exploration program described by Roc as the “last roll of the dice” for the offshore Perth Basin project.

The well is interpreted that have intersected a 25m gross hydrocarbon column, of which about 18m is net pay.

Roc said the accumulation appears to have a small gross gas column above an oil column containing light oil in sands of poor to moderate reservoir quality.

The company speculated the structure could contain between 20 million and 40 million barrels of oil in-place.

Managing director John Doran said the exploration program had provided enough success to move each of the three discoveries into the appraisal stage.

“It is always nice to drill three offshore exploration wells and make three discoveries, particularly when that extends the known oil and gas fields some 200km along regional strike to the northwest of the Cliff Head oil field,” he said.

“However, at the end of the day we’re not looking to play with exploration success statistics, but rather to clock up commercial success – and it will take some time to establish whether or not we have done that.”

Of the three discoveries, Doran said Frankland and Dunsborough had the best chance of being developed, while Perseverance would “probably need a lot of good things to happen around it if it is going to make the grade”.

“Whatever the details, it would seem that an exploration program that was regarded by Roc as the last throw of the dice in the northern offshore Perth Basin, has certainly provided enough success to cause us to move the discoveries on to the appraisal stage and continue to explore around and on trend from them.”