The two Australian companies were paid $A123 million each, valuing the project at $A1.23 billion.

Anzon and Beach, which hold 50% stakes, will retain a 40% participating interest in the project.

Anzon will remain operator.

The new participant in the joint venture will be Cieco Exploration and Production (Australia) Pty Ltd, a wholly owned subsidiary of Itochu and a partner in Western Australia's Cliff Head oil development.

Beach managing director Reg Nelson said Itochu would bring “significant technical and financial strength” to the joint venture.

Anzon executive chairman Steve Koroknay agreed.

“The Itochu Corporation is a highly respected international organisation built on strong global investments.

“Their input not only inspires confidence in our operation but provides unique opportunities for Anzon to grow internationally.”

The BMG project was developed to initially produce oil from the Basker and Manta fields, based on initial proved and probable (2P) reserves estimates of about 23 million barrels (MMbbl).

But new wells drilled in 2006 expanded the reserves base with 2P oil reserves standing at nearly 40MMbbl, while an associated increase in the natural gas resource has nearly quadrupled estimates of the gas-condensate resource.

Up to six new wells are scheduled to be drilled in the fields, starting with Basker-6 early in 2008.

However, the project has had some glitches. Most recently, damage to the Basker Spirit shuttle tanker has seen production fall and repair work delayed until mid September.

On completion of the Itochu farm-in, the participants in the Basker Manta Gummy Joint Venture will be: Anzon Australia 40% (operator), Beach Petroleum 40% and Cieco Exploration and Production (Australia) Pty Ltd 20%.