The first pipeline would stretch for 900 km (560 miles) from Yulin city in the gas-rich Shaan-Gan-Ning basin to Beijing, via Shijiazhuang, the capital of the northwestern province of Hebei, they said.

It would be able to transport eight billion cubic metres (bcm) of natural gas a year upon completion by the end of 2004, they said.

"The feasibility study would be completed by the end of this year," said one official. "Construction is expected to start next year and to be completed by late 2004".

PetroChina also planned to build a branch pipeline to Cangzhou city in Hebei province, where it would link up with an existing gas pipeline to the neighbouring province of Shandong, they said.

Shaan-Gan-Ning basin, one of China's largest gas discoveries so far, has recoverable proven gas reserves of over 500 bcm.

A Shell official told Reuters his company and PetroChina were conducting a pre-feasibility study on a gas pipeline from Changbei Field - also in Shaan-Gan-Ning basin - to Beijing and Hebei that it might stretch to Shandong province.

A feasibility study was likely to be carried out later this year, and the $800 million pipeline was expected to deliver up to three bcm natural gas annually, the official said.

These two pipelines would ensure natural gas supply to Beijing over the next few years amid rapid economic growth.

It would also gel with a government push to use environmental-friendly energy as promised in their bid to host the 2008 Olympic Games.

Some officials predicted gas consumption would exceed at least three bcm in Beijing in 2005 and was set to see rapid growth ahead of the 2008 Olympics.

PetroChina's first Shaanxi-Beijing gas pipeline, which began operations in 1997, has a maximum capacity of three bcm gas a year.

It provided 1.885 bcm of natural gas to Beijing last year, but could hardly meet demand in winter when gas was used for household heating.