TOKYO, May 9 (Reuters) - Japan's Osaka Gas Co (9532.T: Quote, Profile, Research) said on Friday it has entered into a 6-year purchase agreement starting from April 2009 with the North West Shelf LNG venture off Australia for about 500,000 tonnes of liquefied natural gas (LNG) yearly.

The new contract comes after a 20-year contract to purchase about 790,000 tonnes of LNG a year from the joint-venture ends March 2009.

In addition, Japan's second-largest city gas provider previously entered into a 30-year contract from April 2004 to purchase around 1 million tonnes of LNG a year from the joint-venture.

The six equal partners in the North West Shelf joint-venture are Woodside Petroleum Ltd (WPL.AX: Quote, Profile, Research) , BHP Billiton Plc/Ltd (BHP.AX: Quote, Profile, Research) (BLT.L: Quote, Profile, Research), Chevron (CVX.N: Quote, Profile, Research), BP Plc (BP.L: Quote, Profile, Research), Royal Dutch Shell Plc (RDSa.L: Quote, Profile, Research) (RDSb.L: Quote, Profile, Research) and Japan Australia LNG (MiMi) Pty Ltd, which is a joint venture of Mitsubishi Corp (8058.T: Quote, Profile, Research) and Mitsui and Co (8031.T: Quote, Profile, Research).