PetroChina Company Limited, together with its subsidiaries, engages in a range of petroleum related products, services, and activities in Mainland China and internationally. It operates through Exploration and Production, Refining and Chemicals, Marketing, and Natural Gas and Pipeline segments. The Exploration and Production segment engages in the exploration, development, production, and marketing of crude oil and natural gas. The Refining and Chemicals segment refines crude oil and petroleum products; produces and markets primary petrochemical products, derivative petrochemical products, and other chemical products. The Marketing segment is involved in marketing of refined products and trading business. The Natural Gas and Pipeline segment engages in the transmission of natural gas, crude oil, and refined products; and sale of natural gas. As of December 31, 2017, the company had a total length of 82,374 km, including 51,315 km of natural gas pipelines, 19,670 km of crude oil pipelines, and 11,389 km of refined product pipelines. It is also involved in the exploration, development, and production of oil sands and coalbed methane; trading of crude oil and petrochemical products; storage, chemical engineering, storage facilities, service station, and transportation facilities and related businesses; import and export of goods and technology; and import and export agency business, as well as provision of technology promotion, professional contractor, and main contractor services. The company was founded in 1988 and is headquartered in Beijing, the People's Republic of China. PetroChina Company Limited is a subsidiary of China National Petroleum Corporation.