Chevron Australia and its Gorgon joint venture partners on Tuesday announced the production milestone for the project expansion that began five years ago.
Already one of the world's largest and costliest offshore developments, Gorgon exports liquefied natural gas to Asia and supplies WA with gas.
The $4 billion expansion involved the installation of 11 additional wells in the Gorgon and Jansz-Io fields and offshore production pipelines and subsea structures to maintain feed gas supply for the gas processing facilities on Barrow Island.
Chevron Australia managing director Mark Hatfield said the production of first gas marked the next phase of the project and demonstrated a commitment to providing reliable and affordable energy to the region.
"Importantly, the team completed the complex offshore installation work, totalling more than 3.2 million hours to date, without any serious injuries or incidents," he said.
The seven new wells in the Gorgon field and four wells in the Jansz-Io field are in water depths of between 220 and 1350 metres.
As well as system upgrades on Barrow Island, the offshore installation included more than 46 kilometres of production pipelines and 2840 tonnes of subsea structures.
The Chevron-operated Gorgon project is a joint venture between the Australian subsidiaries of Chevron (47.3 per cent), ExxonMobil (25 per cent), Shell (25 per cent), Osaka Gas (1.25 per cent), Tokyo Gas (one per cent) and Japan's JERA (0.417 per cent).
With a project life span of more than 40 years, the first LNG cargo left Barrow Island in March 2016 and supply to the WA market began in December that year.