The terminal is about 40 kilometres south of PNG and exports crude oil via tanker offloading facilities.
The onshore preparation work will run until the end of this year while the offshore work will last about four months with a planned completion date in April 2012.
Extending the life of the terminal is seen by Clough AMEC as an important component of the PNG LNG project, of which Oil Search has a 29% stake.
The PNG LNG project will produce additional associated liquids which will be exported via the terminal.
Both companies saw the winning of the contract as a tick for the joint capabilities of AMEC and Clough, and added that they will work closely with Oil Search and draw on 26 years' experience in PNG to deliver the project safely and successfully.