PetroChina Co Ltd was established as a joint stock company on November 5, 1999. The Company is engaged is engaged in the exploration, development, production and sales of crude oil and natural gas; the refining of crude oil and petroleum products; the production and sales of basic and derivative chemical products and other chemical products; the marketing and trading of refined products and the transmission of natural gas, crude oil and refined products, and the sales of natural gas. The Company's business is segmented into the following groups: Exploration and Production; Refining and Chemicals; Marketing; and Natural Gas and Pipeline. PetroChina is China's largest producer of oil and gas. The Exploration and Production segment is involved in the exploration, development, production, and marketing of crude oil and natural gas. The Refining and Chemicals segment engages in the refining of crude oil and petroleum products; and production and marketing of primary petrochemical products, and derivative petrochemical products and other chemical products. The Marketing segment is involved in the marketing of refined products; and trading activities. The Natural Gas and Pipeline segment engages in the transmission of natural gas, crude oil, and refined oil products. The Company competes in its business segments both in China and in international markets. Its competitors include China Petroleum and Chemical Corporation, or Sinopec, including its subsidiary, China National Star Petroleum Corporation, or CNSPC, and CNOOC. The Company is subject to numerous national, regional and local environmental laws and regulations and environmental regulations promulgated by the governments in whose jurisdictions it has operations. These laws and regulations consist of oil and gas exploration and production operations, petroleum and petrochemical products and other activities.