It marks a big achievement in the commissioning and start-up phase of the project.

Propane and ethylene play a key role in the Optimized Cascade process, the liquefaction technology owned by APLNG shareholder ConocoPhillips.

It will take several weeks to load the refrigerants, which will cool and compress the gas that will come from the state's sprawling CSG fields.

Australia Pacific LNG CEO Page Maxson, said that substantial effort had been placed on completing safety control systems and commissioning the ground flare prior to refrigerants arriving on site.

"The arrival of the refrigerants signifies a key step toward starting up the first LNG train. It enables us to meet the next milestones including test runs of the compressors, followed by final commissioning of remaining units of the first LNG train.

"Today's achievement keeps us firmly on track for first LNG export in the second half of this calendar year," Maxson said.

Australia Pacific LNG continues strong performance in the delivery of the project, with the LNG facility firing up its gas powered generators in April, and the first phase of development and infrastructure in the gas fields nearing completion.

Sinopec, which is a 25% partner in the project, is the main customer for the plan.

Sinopec is contracted to take almost all of the 8.6 million tonne per annum output of APLNG, however the Asian gas market is in a glut and gas prices are falling, and there has been recent speculation the company doesn't need the gas and will try to sell much of it on the spot market given it is under a take-or-pay agreement.

Origin and ConocoPhillips each have 37.5% in the project.