China's largest oilfield, the Daqing oilfield in Heilongjiang Province, northeast China, has maintained a steady level of crude oil output in the first quarter of this year despite a decrease in its natural reserves, a senior company official has said.

"The oilfield pumped out more than 10.6 million tons of crude oil and 670 million cubic meters of natural gas in the first quarter, basically the same as that of the same period last year," said Sui Jun, deputy general manager of the Daqing Oilfield Co. Ltd, a wholly-owned subsidiary of PetroChina.

"It laid a solid foundation for us to achieve our target of producing more than 43 million tons of oil this year," Sui said.

The ageing Daqing oilfield, which has been in operation for 47 years, reached a peak in its output in 1975, producing more than 50 million tons a year. It maintained this level until 2003.

It produced 43.41 million tons of crude oil last year, down 3.4 percent from 2005.

To offset its falling output, the company has started to make full use of associated gas - a natural gas which is found in association with crude oil either dissolved in the oil or as a cap of free gas above the oil.

More than 800 million tons of natural gas reserves have been discovered in northeast China, the Daqing Oilfield Co. Ltd. confirmed on Tuesday.