Daqing Oilfield Co., the largest oil subsidiary of PetroChina, produced 20.07 million tonnes of crude oil in the first half, the company said Friday.

Natural gas output reached 1.66 billion cubic meters in the same period, it said in a statement.

Last year, its crude production was 40 million tonnes and gas output 3 billion cubic meters.

Daqing oilfield, which was discovered in 1959, has maintained an annual crude output at around 40 million tonnes since 2008, and gas output has grown steadily.

China's largest oilfield saw crude output fall to 48.4 million tonnes in 2003, the first time it was below the 50-million-tonne level in 27 years.

PetroChina is the listed arm of China National Petroleum Corporation (CNPC), the country's largest oil and gas producer.