China's Bohai Bay may have reserves of 20 billion tons of oil, with half of them still undiscovered, said Zhai Guangming, an oil exploration expert with the Chinese Academy of Engineering.

The Bohai Bay rim was estimated to have about 60 basins similar to the newly found Jidong Nanpu oilfield, said Zhai, who is also the first manager of the Jidong Oilfield Co. under China National Petroleum Corporation (CNPC),

Zhai's remarks were echoed by Xia Yishan, an expert with the National Energy Leading Group, who said, "Given the geological structure in the regions surrounding the Bohai Sea, more oilfields will be discovered".

CNPC, the country's biggest oil and gas producer, says the newly found oilfield, with a reserve of 1.02 billion tons of oil, will increase the company's oil reserves by 55 percent and its gas reserves by nine percent.

CNPC has plans to develop the oilfield, with the first-phase project, to be finished by 2012, yielding 10 million tons per year.

Output is expected to rise progressively to 25 million tons a year, making it China's third largest field after Daqing and Shengli.

Considering the environmentally sensitive areas near the Bohai Sea, the oilfield was expected to become China's first "green oilfield", with all discharges properly treated and waste recycled, said CNPC vice president Hu Wenrui.