The potential for commercialising the Gorgon field was questioned in the late 1990s as the gas was classed as "dirty" due to it containing a high percentage of carbon dioxide.

A few years later, Chevron announced its ambitious carbon sequestration plan, which was applauded by various politicians and planned to be running by 2015.

But a series of delays and cost blowouts delayed first gas production until March 2016, and finally on Thursday, the US giant said the carbon capture system had begun working.

Richie Merzian, climate and energy program director with think tank The Australia Institute said "better late than never".

Chevron was required to sequester carbon under its development approval and had an "emission-reduction debt" for pollution vented in the years since gas production began, he said.

Conservation Council of WA director Piers Verstegen agreed, saying the company should invest in offsets such as tree planting to make up for it.

Chevron claims that once it is fully operational, the injection system will reduce Gorgon's greenhouse gas emissions by about 40 per cent, which Mr Verstegen says is not enough.

But politicians again lined up to applaud the Chevron-led joint venture.

"This has been a very expensive and complicated proposal that has challenged both the proponents and regulators alike, and having it finally cross the production line must be a relief to all," WA opposition environment spokesman Steve Thomas said.

Chevron Australia managing director Al Williams said it was one of the biggest greenhouse gas mitigation projects ever undertaken by industry.

"We are monitoring system performance and plan to safely ramp up injection volumes over the coming months as we bring online processing facilities," Mr Williams said.

The federal government contributed $60 million towards the $2.5 billion project.

Barrow Island, about 56km off the Pilbara mainland, was declared a Class A nature reserve in 1910 but has hosted onshore oil production since 1964.

Australian Associated Press