When Bill Barrett Corp, a small US natural gas producer, first went to Utah's Nine Mile Canyon in 2002 to begin drilling, it sought permission to drill fewer than 100 wells. But the price of natural gas has rocketed in the intervening years and now Bill Barrett is seeking approval for 800 more.

In the last year alone, Devon Energy, an oil and gas explorer, has grown production by more than one-third to more than 1bn cubic feet equivalent a day in the Barnett Shale, its largest asset and one of the largest gas fields in the US. And, in the past few weeks, BP, the UK oil group, bought about 90,000 acres of natural gas properties in Oklahoma.