The gas field, an estimated 602.5 billion cubic metres in size, will provide sufficient energy support for a considerable period of time for Beijing and Tianjin municipalities, North, East and Central China, Shaanxi and Gansu provinces and the Ningxia Hui Autonomous Region in Northwest China, the Ministry of Science and Technology announced recently in Beijing.

The natural gas field is expected to produce an average 6.5 billion cubic metres per annum in the next five years, said the ministry's secretary-general Shi Dinghuan.

"The field will greatly back up the country's project of west-to-east gas transportation and help ease the energy shortage in eastern areas," said Shi.

The field is expected to supplement natural gas to Beijing and other major cities in eastern areas, reduce coal consumption to a certain degree and, therefore, help minimize air pollution in the cities, according to Qian Kai, a researcher with the Chinese Institute of Oil Exploration.

Beijing consumes an average of 1.4 billion cubic metres of natural gas each year, less than 10 per cent of its total energy resources.

If natural gas accounts for 30 per cent of its total energy consumption, the capital can enjoy fairly good air quality, said Qian.

By 2008, when Beijing embraces the Olympic Games, the capital is expected to use approximately 6 billion cubic metres of natural gas, making up more than 10 per cent of its total energy consumption. Then Beijing's air quality will be considerably improved, said Qian.

He added that this newly discovered gas field will also make China rely less on oil imports from foreign countries.

The gas field is located in the Erdos Basin, described as having a complicated surface. This poses difficulties for scientists to tap the field. However, a technological breakthrough has allowed scientists to reach essential resources, said He Zixin, deputy director of the Changqing Oil and Gas Field Company, which engaged in the field exploration.

The company will be a major performer in transporting gas to Shanghai and the Yangtze River Delta areas as part of the country's west-to-east gas transportation project.

The Ministry of Science and Technology will continue to give support to the exploration of oil and natural gas resources in the next few years to sustain the safety of the country's energy resources, said Vice-Minister Li Xueyong.