HARBIN — Daqing Oilfield, controlled by the China National Petroleum Corporation in Northeast China's Heilongjiang province, has become the world's largest tertiary oil recovery production base, the oilfield said.

The annual crude oil output via tertiary recovery of Daqing Oilfield has exceeded 10 million tonnes for 20 consecutive years, bringing its cumulative total production to 286 million metric tons.

Tertiary recovery, also known as enhanced oil recovery, is the third stage to extract oil from an oil reserve. Through the injection of chemicals, the method exploits the oil that cannot be collected in the primary recovery and secondary recovery stages.

Tertiary oil recovery technology increased the recovery rate of Daqing Oilfield by 14 to 20 percentage points.

At present, Daqing Oilfield not only applies tertiary recovery technology in domestic oilfields, but also provides technical support for Russia and Kazakhstan.