Minister for State Development Clive Brown welcomed the arrival of the vessel, which had been working on the North West Shelf's second trunkline.

At 200 metres long, the Semac is currently Australia's largest offshore construction vessel. While only a relatively minor exercise, it shows the facility can easily deal with the largest vessels at work in the oil and gas construction market.

Brown said the expansion of the North-West Shelf project, the emerging gas processing hub on the Burrup Peninsula and the $11billion Gorgon gas project had the potential to turn the Australian Marine Complex into one of the region's leading fabrication and marine construction precincts.

"WA's gas and gas processing industries are restoring the State's reputation as the engine room of the national economy," Brown said.

The Minister said the strong local content requirements of the Gorgon State Agreement created significant opportunities for contractors at the Australian Marine Complex.

"The Government has required the Gorgon Joint Venture to give proper consideration and, where possible, preference to WA suppliers, manufacturers and contractors when letting contracts or placing contracts," Brown said.

The vessel is expected to be in the AMC for up to a month.