In a preliminary report, Roc said its company-wide 2P reserves now stood at 21.4 mmboe as a result of the Zhao Dong reserves revision.

But the company added that this did not alter the fact that a potential for 10 mmboe of possible reserves, net to the company, was recognised within the block.

Much of this un-risked and unbooked reserve upside will be evaluated as part of the Roc-operated $US500 million development activities currently underway.

Roc’s managing director John Doran said the geology at Zhao Dong was more difficult than first realised.

“While its petroleum potential is self-evident, the geology of the Zhao Dong Block has a touch of the Rubik’s Cube about it,” he said.

“Therefore, it is not entirely surprising that it took – and is still taking – some time to get to grips with the detailed nature of the reservoir nor that the remaining in-place oil resource at Zhao Dong will not be better defined until a major subsurface data review has been completed by year end.

“However, what is already clear is that the magnitude of the in-place oil resource is such that if, over the next ten years, the overall recovery factor proves to be just a few percent better than that which is currently assumed, the 2007 reserves revision would be more than offset.”

Doran said the result was not expected to have any effect on Zhao Dong production performance during 2008, expected to be inline with last year’s levels of 1.7 million barrels net to Roc.

On a positive not, Roc achieved a record annual production result of 3.5mmboe – up 77% on the 2006 result – with 99% of the output being oil.

Based on this result, the company also achieved $248 million in annual revenue – another record, being 64% higher than the previous year, thanks to higher production and strong oil prices.

Elsewhere in China, the company plans to reclassify 3.7mmboe of net resources at its Wei 6-12S oil field, offshore Beibu Gul, into 2P reserves, should the project be declared commercial later this year.