China National Offshore Oil Corporation
In 2009 the corporation was re-incorporated as a limited company. The group also acquired Shanxi Huayu Energy in the same year. China United Coalbed Methane, a joint venture of China Coal Group and PetroChina, became a wholly owned subsidiary of China Coal Group also in 2009. At the same time PetroChina acquired some assets from China United Coalbed Methane. China Coal Group later sold China United Coalbed Methane to China National Offshore Oil Corporation in tranches from 2010 to 2014.