Royal Dutch Shell has started natural gas production from the Changbei gas field in the northern territories of Inner Mongolia and Shanxi as part of a sharing contract with PetroChina, the Wall Street Journal reported. The 1,693-square-kilometer field in which Shell will spend US$600-700 million drilling some 50 wells over the next seven years, is one of the biggest joint ventures in China's oil and gas industry. Much of the gas will be used to meet Beijing's growing energy needs and, as the fuel is a clean-burning alternative to coal, it is hoped it will go some way to easing pollution in the city. The Changbei field is expected to produce 3 billion cubic meters of gas per year.