CNOOC Limited, an investment holding company, explores for, develops, produces, and sells crude oil and natural gas in offshore China, Canada, the United States, the United Kingdom, Nigeria, Argentina, Indonesia, Uganda, Iraq, Brazil, Guyana, Russia, Australia, and internationally. The company operates through three segments: E&P, Trading Business, and Corporate. It produces offshore crude oil and natural gas primarily in Bohai, the Western South China Sea, the Eastern South China Sea, and the East China Sea in offshore China. The company also holds interests in various oil and gas assets in Asia, Africa, North America, South America, Oceania, and Europe. As of December 31, 2020, it had net proved reserves of approximately 5.37 billion barrels of oil equivalent. In addition, the company is involved in the issuance of bonds; sale and marketing of petroleum and natural gas; and surface exploration and sale of coalbed methane. The company was incorporated in 1999 and is based in Central, Hong Kong. CNOOC Limited is a subsidiary of China National Offshore Oil Corporation.