The value of a contract held by Leighton Holdings for work on the Gorgon natural gas project has more than doubled to nearly $1.8 billion.
Leighton said changes had been made to reflect an increased scope of work that provides more flexibility and faster delivery.
Leighton Contractors is carrying out earthworks and installing concrete and underground drainage, pipes and cables at the massive project.
The company began the work September 2010 under a contract worth just over $800 million.
Leighton said today the changes to the contract take its value to $1.789 billion.
In December, project operator Chevron increased its cost estimates for the Gorgon project, located on Barrow Island off WA's northern coast, from $43 billion to $52 billion.
Chevron advised today that the increased cost of the Leighton contract was included in the revised budget.