The investment will expand coal seam gas production in Queensland state and go towards the construction of a 540 kilometre (335-mile) underground pipeline linking the gas fields to a LNG plant.
BG Group is among several companies seeking to convert Queensland's rich coal seam gas deposits into LNG for export to meet surging Asian demand.
"The project will have an operating life of at least 20 years," BG Group executive vice president Catherine Tanna said.
"We have scheduled LNG shipments in 2014 and we have binding commitments with LNG customers in China, Japan, Singapore and Chile, and we will also continue to provide gas to markets in eastern Australia."
Australia's Acting Prime Minister Wayne Swan said the project would deliver a boost to the Australian economy.
"It marks an important and exciting leap ahead in the development of Australia's vast coal seam gas reserves -- reserves that in Queensland alone are estimated to be enough to power the whole state for more than 500 years," he said.
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