PetroChina Daqing Oilfield, a subsidiary of PetroChina, produced 40 million tons of crude oil in 2012, the China National Petroleum Corporation said.

This is the tenth consecutive year for the country's largest oil field to yield more than 40 million tons of crude oil, according to the CNPC, the parent of public-listed PetroChina.

Previously, the oil field had seen annual output exceed 50 million tons, but output shrank due to harder operations in oil exploitation, according to the CNPC, the country's largest oil producer and supplier.

The oil field aims to secure annual crude oil production of 40 million tons during the 12th Five-year Plan period (2011-2015).

In 2012, Daqing also produced 3.3 billion cubic meters of natural gas. And the oil field added 55.35 million tons of proven oil reserves.

Discovered in 1959, Daqing is located in northeast China's Heilongjiang province.

China consumed 450 million tons of crude oil in 2011, 250 million tonnes of which were imported, and both the oil consumption and the oil import ratio will continue to rise, according to the CNPC.