Chevron has marked a major milestone of construction of the $US29 billion ($37 billion) Wheatstone project with the installation of the platform topsides off the Pilbara coast.
The US oil and gas giant says the milestone marked the biggest single integrated topsides float-over installation Chevron has ever completed.
"The Wheatstone platform will be the largest offshore gas processing platform ever installed in Australia, with a topsides weight of about 37,000 tonnes and the largest float-over installation Chevron has ever delivered globally," a spokesman said.
The topsides are 28m above sea level and were designed to withstand 12-storey waves.
In another first for Chevron, the Wheatstone platform has used a steel-based substructure, to support the topsides, for the first time.
The spokesman said the steel base had resolved technical foundation design challenges and provided cost savings over other alternatives.
Construction of the overall Wheatstone project, centred on a two-train processing plant near Onslow with an installed capacity of 8.9 million tonnes of LNG annually, is almost 60 per cent complete.
The namesake Wheatstone fields, which will dominate supply to the Onslow plant, are about 200km off the coast.
Chevron is targeting first gas by the end of next year.