The biggest oil discovery in the country for a decade will contribute more proven reserves in five to six years, PetroChina's chief geologist has said.

We estimate that, eventually, we could have proven reserves of as much as 1 to 1.6 billion tons (oil equivalent) from the offshore blocks of our Jidong Nanpu oilfield in the Bohai Bay area," Jia Chengzao, vice-president of PetroChina and academician at the Chinese Academy of Sciences, told the China Oil and Gas forum on Saturday.

"Including reserves from onshore, the ultimate proven reserves of Nanpu oilfield are expected to hit around 2 billion tons."

The Jidong Nanpu oilfield has combined proven, probable and possible reserves of 1.18 billion tons of oil equivalent, the Ministry of Land and Resources certified in August. The present proven reserves are certified at 445 million tons oil equivalent.

It may take approximately five to six years to confirm the new reserves, and exploration efforts will be made simultaneously with extraction work on current proven reserves, Jia told China Daily on the sidelines of the forum.

"Clearly at Nanpu, the offshore sector boasts larger potential than the onshore part To reach the 10 million ton annual output target by 2012, the current proven reserves are enough," Jia said.

Zhai Guangming, a renowned geologist with the Chinese Academy of Engineering, recently said current exploration efforts have tapped less than half of Bohai Bay's potential.

As exploration goes deeper, more oil and gas discoveries will be made to partly meet surging local energy demand, Wang Tao, chairman of China National Committee of World Petroleum Council, said at the forum.

Official estimates show that the country may boast 65 billion tons of oil reserves, and about 25 trillion cubic meters of natural gas.

But the problem is that only a small percentage have been proven, according to Wang, former minister of the petroleum industry.

If even half of the resources are exploited, the reserves will jump," Wang said.

The geologist revealed that recoverable oil resources stand at 25.5 billion tons, with only 7.363 billion proven.

"The proven rate is low and there is still a large potential to tap, which means it is still possible for giant oilfields to be found," Jia said.

More locally produced oil and gas will reduce dependence on energy imports.

Net oil imports rose 4.1 percentage points year on year to 47 percent of total consumption last year, according to the Ministry of Commerce.

Last year, the nation produced 183.68 million tons of crude oil, up 1.7 percent, and imported 138.84 million tons, up 16.9 percent. Oil consumption (crude plus oil products) amounted to 346.55 million tons, up 9.3 percent.