(Corrects paragraph 6 to show third new LNG train being planned by Exxon Mobil, not by Total-led project)

* Deal allows initial work to kick off on project -Oil Search

* Final Investment Decision expected in 2020 -Oil Search

* Overall expansion of PNG’s LNG output expected to cost $13 bln

April 9 (Reuters) – Australia’s Oil Search, France’s Total SA and Exxon Mobil on Tuesday signed a deal with Papua New Guinea that will allow work to start on a long-awaited project which could help double the nation’s liquefied natural gas exports.

Oil Search said in a statement that the agreement would allow the parties to start activities related to so-called Front End Engineering and Design (FEED) such as contractor selection for Papua LNG