CNOOC Limited is an investment holding company. The Company, along with its subsidiaries, is a producer of offshore crude oil and natural gas and an independent oil and gas exploration and production company. Its subsidiaries are engaged in exploration, development, production and sales of oil and natural gas, as well as other petroleum products. It has three segments: independent operations, operations under joint arrangement and trading business. The Company has four producing areas in offshore China, which include the Bohai Bay, Western South China Sea, Eastern South China Sea and East China Sea. It also has oil and gas assets in Indonesia, Iraq, Australia, Africa, North America and South America. As of December 31, 2011, its subsidiaries included CNOOC China Limited, CNOOC International Limited and others. On July 20, 2011, it acquired OPTI Canada Inc, through its indirect wholly-owned subsidiary, CNOOC Luxembourg S. r.l. In February 2013, the Company acquired Nexen Inc.