In a statement, the global oil and gas giant said it had signed a deal with offshore drilling contractor Atwood Oceanics for a rig that is about to start being built at the Jurong shipyards in Singapore.

The minimum three-year contract between the two companies will be worth at least $450 million, with an option to extend it by an additional three years.

Chevron said the new rig would be able to moor in up to 6000 feet of water with its own mooring equipment and could work in up to 8000 feet of water with pre-laid moorings.

Atwood estimated the total cost of the rig – including administrative and overhead costs and capitalised interest – would be $US570 million to $US590 million.

Chevron Australia said the Atwood contract was significant and underpinned its long-term commitment to find, appraise and develop Australian gas resources for domestic and international markets.

The new rig, expected to be operational in the second half of 2011, will be used in the Greater Gorgon area northwest of Barrow Island, which is estimated to contain up to 40 trillion cubic feet of gas.