The partners are targeting a large structure in Western Australia's Barrow Sub-basin that could hold about 1 trillion cubic feet of gas and 20 million barrels of recoverable condensate, junior partner Tap Oil said yesterday.

"Marley-2 is adjacent to existing joint venture infrastructure and [has] the potential to more than double Tap's reserves," Tap said.

Located in the Harriet JV's TL/5 permit, Marley-2 is in about 43m of water roughly 3.5km west-southwest of the Campbell platform and 143m north of Marley-1, where drilling was halted in January 2006 due to mechanical problems.

Marley-2 is a vertical well designed to test Jurassic sandstones that Marley-1 failed to reach.

Drilling is estimated to take about 48 days to reach an expected total depth of 4100m subsea.

The Harriet Joint Venture comprises Apache Northwest (operator and 68.5%), Kufpec Australia (19.2771%) and Tap (12.2229%).