PetroChina worth US$1tn

Chinese oil and gas company PetroChina has beaten its US rival ExxonMobil to become the world's biggest firm after its first day of trading on the Shanghai stock exchane.

The company now has a market value of about US$1tn - almost double that of oil major Exxon Mobil at US$488bn.

PetroChina was established as a joint stock company in 1999, as part of the restructuring of state controlled China National Petroleum Corporation (CNPC).

It currently invests in exploration, development and production of oil and natural gas, refining operations and the import and export of crude oil.

By staff writer