TAP Oil has started drilling works at the Tallaganda-1 exploration well in the Carnarvon Basin off the Western Australia coast.

Semi-submersible drilling rig Atwood Eagle is being used to drill the well in the WA-351-P permit and target 0.8 to 1.3 trillion cubic feet of gas.

Tap Oil managing director/CEO Troy Hayden said: "We are pleased to have commenced the Tallaganda-1 well which has the potential to deliver a resource multiple times larger than Tap’s current 2P reserves. Success at Tallaganda-1 will also give greater certainty as to the prospectivity of the Triassic potential on the permit."

Drilling is expected to test the gas potential of sandstones in the prolific Triassic age, Mungaroo Formation, in a well defined horst block seen in modern 3D seismic data.

Atwood Eagle will drill the vertical well in a water depth of 1,141m and is expected to take 37 days to drill with a projected total depth of 4,250m.

Tap Oil’s drilling cost is estimated at $10m, following Tap’s farmout of 25% of its participating interest in the permit to BHP Billiton Petroleum last year.

BHP Billiton Petroleum, the operator of the well, owns a 55% stake, Apache Northwest holds 25% and Tap (Shelfal) owns 20%.