Inpex Holdings Inc (1605.T: Quote, Profile, Research), Japan's biggest oil and gas explorer, has raised the reserves estimates for its Ichthys liquefied natural gas (LNG) project off Western Australia, the Australian government said.

Reserves for the Ichthys field, located in the Browse Basin, now stand at 12.8 trillion cubic feet (tcf) of gas and 527 million barrels of condensate, Australia's minister for resources and energy, Martin Ferguson, said in a statement issued late on Tuesday.

"At 527 million barrels, this is the largest liquid hydrocarbon accumulation found in Australia since the Bass Strait in the 1960s," Ferguson said in a statement.

Inpex has previously forecast proven and probable reserves at Ichthys at 9.5 tcf of recoverable gas and 312 million barrels of condensate.

Inpex and project partner Total (TOTF.PA: Quote, Profile, Research) of France are obtaining environmental approvals to build a LNG plant for Ichthys gas either in the Maret Islands in the Kimberley region of Western Australia, or on Middle Arm in Darwin in the Northern Territory.

Initial LNG output of the project is set to top 8 million tonnes a year, in addition to 1.6 million tonnes per year of liquefied petroleum gas (LPG) and up to 100,000 barrels per day of condensate.

First LNG output has been delayed to 2014, from an original plan of the end of 2012, Inpex said earlier this month.

Inpex has a 76 percent stake in the field, while Total owns the rest.