China will build its first underground natural gas storage facility in north China's Dagang Oilfield, the country's sixth-largest oil production base, in a bid to adjust the seasonal gas supply for Beijing, according to the China National Petroleum Corp (CNPC).

The project consists of an underground gas storage, an above ground gas treatment plant and compression plant, as well as gas pipelines, with an investment of 1.3 billion to 1.5 billion yuan, said Zhang Yu, manager of the Underground Storage Division under Beijing Gas Transmission Co.

Gas pipelines between Beijing and the underground storage facility are under construction and will be completed by this December, while the entire project will be put into operation by November next year, he added.

The underground facility, actually not a man-made underground gas tank but a gas-bearing stratum, covers an area of 5.7 square kilometers at a depth reaching 2,650 meters, said He Xian, vice- dean of the Drilling and Exploitation Institute of the Dagang Oilfield.

Dagang is suitable as a site for underground storage thanks to its stable geologic structure and large storage volume, he added.

The underground storage will hold about 1.6 billion cubic meters of gas, some one billion cubic meters of which will act as an air bed to provide enough pressure for exploitation, he said.

He pointed out that with this underground facility, at least 600 million cubic meters of gas, which remains idle in summer, can be stored there and exploited again in winter when needed.

According to the official source, Beijing consumed only 270,000 cubic meters of gas daily between April and June in 1998, while its highest daily gas consumption in winter topped 3.22 million cu m.

Underground storage has proved to be an efficient way to adjust the seasonal gas supply for big cities and is widely used in many countries, while underground storage in Dagang is the first of its kind in China. (Xinhua)