The Changqing oil field is an oil field located in Inner Mongolia. It was discovered in 1971 and developed by China National Petroleum Corporation. It began production in 1975 and produces oil and natural gas. The total proven reserves of the Changqing oil field are around 23.8 billion barrels (3400×106tonnes), and production is centered on 472,000 barrels per day (75,000 m3/d). Changqing is the largest oil and gas field in China.