The South Korean Ministry of Knowledge Economy has approved Kogas' plans to buy 3.64MMtpa from Prelude for 20 years starting from 2017, which also represents the entire planned LNG capacity of the project, and 2MMtpa of LNG from Total's share of the Inpex-operated Ichthys LNG project and other projects in Nigeria, Norway and Egypt between 2014 and 2031.
Kogas will also take up a 10% stake in Prelude and prior to its start-up will buy 1MMtpa of LNG from Shell's other fields in Russia and Nigeria beginning 2013.
"The deals are expected to greatly help stabilise the country's LNG supplies when global concerns about short supplies are flaring following the earthquake in Japan in March," the ministry said in a statement.
Kogas is expected to formalise the deals, worth about $A80 billion, in September, the AAP reported.
South Korea's LNG demand has been growing on the back of stronger power demand driven by economic recovery, with the country importing 32.6MMtpa of LNG last year.
Kogas' monthly gas sales have been increasing on a yearly basis since August 2009, except in October 2009.