After months of speculation, partners ConocoPhillips, Origin and Sinopec agreed FID and Sinopec agreed to take another 10% equity interest in the project for $US1.4 billion ($A1.36 billion).
Origin said both it and ConocoPhillips were now looking to further dilute their stake from 37.5%, with Origin telling the media it would seek to retain around a 30% slice of the project.
First LNG from the project is on track for 2015 while first LNG from the second train is expected from 2016.
FID had been expected shortly after Origin signed a 20-year 1 million tonne per annum offtake deal with Kansai Electric late last week.
While Kansai agreed to a 1.1MMtpa offtake deal, Sinopec's total offtake has now grown to 7.6MMtpa after the second train FID.
The agreement follows on from the signing of a heads of agreement last November and is conditional upon APLNG making a FID on a second train for the project.
APLNG flagged FID by mid-2012 while last week Macquarie Equities said the go-ahead for a second train was imminent, placing a "soft" deadline of June 30.
The APLNG JV has also been busy this year arranging finance for the project, penning an $8.6 billion facility from a syndicate of banks, including the export-import banks of China and the US for the downstream segment of the project.
The facility was subject to the APLNG JV reaching FID on the second train of the project.
Origin played down the prospect of further cost increases at the project which had been plaguing other LNG projects in Australia, telling investors the cost of the project had not changed, aside from foreign exchange movements.
It said project economics were "robust", with a break-even oil process of $35 per barrel over project life to cover all estimated project costs and an oil price of $50/bbl allowing Origin to recover its weighted average cost of capital on its cash injection into the project.
Origin managing director Grant King hailed the FID as a major milestone for the project and for Origin.
"As one of Australia's largest LNG export projects, the Australia Pacific LNG project stands to deliver significant value to Origin shareholders and to Australia, as well as jobs for the Australian community," he said.
"The incremental benefit of the second LNG train will strengthen the project's already robust economics."
