LANZHOU, Oct. 18 (Xinhua) -- The annual production of oil equivalent of crude oil and natural gas at PetroChina Changqing Oilfield Company, a subsidiary of China's top oil-and-gas producer PetroChina, is expected to pass the 60-million-tonne mark in 2020.

Located in northwest China's Erdos basin, Changqing Oilfield, with 50 years of history, is China's largest oil-and-gas field and has played an important role in safeguarding the country's energy security.

The oil-and-gas fields of Changqing Oilfield cover Shaanxi, Gansu and Shanxi provinces, as well as Ningxia Hui Autonomous Region and Inner Mongolia Autonomous Region.

The company has produced 46.7 million tonnes of oil equivalent of crude oil and natural gas so far this year, according to Fu Suotang, general manager of PetroChina Changqing Oilfield Company.

Its oil-and-gas output reached 57.03 million tonnes of oil equivalent last year, the seventh consecutive year above the 50-million-tonne level.

PetroChina Changqing Oilfield Company has been carrying out long-term research on geological theories and developing core and key technologies over the past decades, Fu noted.

The company's total proved oil reserves have reached 5.5 billion tonnes, with 3.8 trillion cubic meters of proved natural gas reserves. It expects to produce 63 million tonnes of oil equivalent of crude oil and natural gas in 2025.