The contract is expected start in late 2009, providing Origin with a smooth transition from its current Gascor contract.

Origin chief operating officer Karen Moses said the contract would significantly contribute to meeting Origin's retail gas demand in southeastern Australia.

"Together with our current equity gas reserves, the contract will help service customers across southeastern Australia and potential new generation projects such as Origin's proposed Mortlake Power Station," she said.

The company's BassGas development contributes 20PJ of gas to the company's supply, while the Otway Gas project is expected to contribute an additional 30PJ a year when fully operational.