China National Petroleum Corporation (CNPC), one of China's largest oil producers, will invest 40 billion yuan (US$5.17 billion) in the newly-founded Nanpu Oilfield in the coming five years, says president Jiang Jiemin.

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This is the first time CNPC announced an investment plan for the oilfield. Investors were worried the excessive investment in the block would affect CNPC's overall performance. But CNPC said this year's oil expenditure budget is 185.7 billion yuan, up from 148.7 billion yuan from 2006.

Earlier media reports said the newly found oilfield in Bohai Bay has a reserve of one billion tons, or about 7.35 billion barrels, the largest discovery in the country in the past four decades. But latest explorations indicate Jidong Nanpu Oilfield in Bohai Bay may have more reserves than previously estimated, PetroChina President Jiang Jiemin said yesterday.

"The Jidong Nanpu Oilfield has huge and quality reserves of up to 5 million tons per square km. The 1-billion-ton reserve announced earlier is not the final figure. As our explorations deepen, we expect to discover more reserves," Jiang said.

According to CNPC's estimates, by 2012 the Nanpu Oilfield could produce 10 million tons of crude every year, with 7 million tons coming from offshore areas. After further tapping the Nanpu block.

The investment announcement may make Fidelity Investments regret its decision to sell its PetroChina shares, a subsidiary of CNPC, according to Beijing Times.

But Berkshire Hathaway, an investment company run by the American legendary stock investor Warren Buffett, rejected a proposal to sell its PetroChina shares.

Jiang also said CNPC will go public on China's A-share market, but did not announce when this would happen. He added that CNPC will not issue A-shares when the stock market is overheated.

The demand for fuel in China has increased with the rapid growth of its economy. Last year, the country consumed more than 320 million tons of crude, an year-on-year increase of 7.1 percent, according to the National Bureau of Statistics (NBS).

Last year, 145.18 million tons of crude - or 45 percent of the total crude consumption - was imported, Xinhua News Agency has said, quoting NBS figures.

General Administration of Customs (GAC) data show that China imported a record 14.82 million tons of crude in April, up 23 percent year-on-year. Crude imports rose 10.8 percent year-on-year in the first four months of this year to reach 54.46 million tons.

In contrast, the country's crude exports from January to April fell 55 percent year-on-year to 1.07 million tons, according to customs figures.

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