The Shelf project has supplied Korea with several spot cargoes since export LNG production commenced in 1989 - more recently four cargoes totalling 220,000 tonnes, to be supplied this quarter.

It is understood the move to a longer term arrangement is prompted by an energy supply crisis in South Korea.

While Kogas has refused to indicate when the deal will be finalised, it is understood a deal will be signed in a matter of days. Project operator Woodside has refused to comment on the sale.