CNOOC Limited operates as an investment holding enterprise, primarily engaged in the exploration, development, extraction, and commercialization of crude oil and natural gas. Its extensive global operations cover offshore China, alongside a significant international presence in countries including Canada, the United States, the United Kingdom, Nigeria, Argentina, Indonesia, Uganda, Iraq, Brazil, Guyana, Russia, and Australia. The company's activities are managed across three distinct business segments: Exploration & Production (E&P), Trading, and Corporate functions. Domestically, its principal offshore sites for crude oil and natural gas production are situated in the Bohai Sea, the Western South China Sea, the Eastern South China Sea, and the East China Sea. Furthermore, CNOOC Limited possesses stakes in numerous oil and gas ventures spanning various continents such as Asia, Africa, North America, South America, Oceania, and Europe. As of December 31, 2019, its net proven reserves were reported to be approximately 5.18 billion barrels of oil equivalent. Beyond its core upstream business, the company also participates in financial activities such as bond issuance, the marketing and distribution of petroleum and natural gas, and the surface exploration and sale of coalbed methane. Established in 1999, CNOOC Limited maintains its head office in Central, Hong Kong, and is a subsidiary of China National Offshore Oil Corporation.