Origin Energy Ltd and U.S.-based ConocoPhillips Co' stakes in the LNG project would be reduced to 37.5% each, sources reported.
Sinopec Group also agreed to increase the purchase by 3.3 million tons per year in the LNG project through to 2035, following an earlier agreement to buy 4.3 million tons of LNG per year in the same project for 20 years from 2015.
The first phase of the LNG project would cost A$20 billion, said Origin Energy without disclosing details about the second phase.
At present, the Australia Pacific LNG project meets 40% of the LNG demands in Queensland, Australia.
Australia's Ministry of Resources has estimated that the country would overtake Qatar as the world's top LNG supplier after new projects are developed.