XI'AN, Nov. 18 (Xinhua) -- PetroChina Changqing Oilfield Company, a subsidiary of China's top oil and gas producer PetroChina, is expected to produce 57 million tonnes of oil equivalent of crude oil and natural gas in 2019.

Changqing Oilfield, the country's largest oil and gas field, plays an important role in ensuring the country's oil and gas security.

By Sunday, its oil and gas output had reached 50 million tonnes of oil equivalent this year, the seventh consecutive year that production reached the 50-million-tonne level.

The oilfield, located in northwest China's Erdos basin, has applied new technologies to boost production and extend the life cycle of crude oil and natural gas wells.

The company has also stepped up exploration work. This year, it discovered the Qingcheng oilfield in northwest China's Gansu Province with a proven shale oil reserve of 358 million tonnes and an estimated reserve of 693 million tonnes.