Origin Energy and US giant ConocoPhillips, owner of the A$23 billion ($23.6 billion) Australia Pacific LNG (APLNG) project, along with China Petrochemical Corp. (Sinopec), has approved on Wednesday a final investment decision on the second of its two-train coal seam gas (CSG) to LNG project.

The development effectively increases Sinopec's ownership to 25 per cent from 15 per cent in the project.

The three owners will construct a major transmission pipeline to deliver CSG to processing plants on Curtis Island off the coast of Gladstone. The CSG will then be frozen and converted to LNG for export.

The decision to build the first compressor plant occurred in mid-2011, however the partners postponed its decision on the second.

The first plant is expected to go online in 2015, with the second plant expected a year later.

At least 2,000 workers are needed to build the second plant. They will be added to the current existing 4,000-strong workforce.

Once complete, 1,000 workers will be needed to run, manage and maintain the plants. Each has a production capacity of 4.5 million tonnes per annum.

"It will be a very, very substantial employer," The Australian quoted Grant King, Origin managing director and APLNG chairman, as saying.

First LNG is expected to be shipped in mid-2015 to Chinese and Japanese customers.

With more than $US175 billion new terminals currently being built by global energy heavyweights, such as Chevron Corp and Royal Dutch Shell, Australia no doubt has the capacity to overtake Qatar as the world's biggest LNG source and exporter by end of the decade.