HARBIN, Aug. 4 (Xinhua) -- Daqing Oilfield Co. Ltd., a subsidiary of China's largest oil producer PetroChina, has produced around 21.59 million tonnes of oil equivalent in the first half of 2019.

The oilfield's domestic facilities churned out about 15.48 million tonnes of crude oil and around 2.3 billion cubic meters of natural gas during the period.

In recent years, the firm has been seeking to increase its natural gas output with rising difficulties in extracting crude oil at its main production base, Daqing Oilfield.

The firm has seen a sustained growth of its domestic market share while its overseas market share steadily expands. In the first half of this year, the company's overseas market revenue reached about 7.82 billion yuan, up 6.6 percent year on year, the company said.

Daqing Oilfield, the largest oilfield run by PetroChina in northeast China's Heilongjiang Province, was discovered in 1959.