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

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

Previously, the oil field had seen annual output exceed 50 million tonnes, 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 tonnes 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 tonnes of proven oil reserves.

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