Estimates of the amount of oil they contain vary hugely, but Navigant, a consultancy, reckons that North America could produce anything from 26.9 - 53.5 trillion cubic
metres of shale gas alone, enough to satisfy the world's total current demand for gas for up to 15 years, though at today's prices not all of it would yet be worth extracting.
The British Geological Survey (BGS) recently estimated that the UK has 150 billion cubic
metres of shale gas, about half of its more conventional reserves.
Interest is swelling in the UK, and the British Geological Survey recently released a report estimating that the north of England has around 35 trillion cubic
metres of shale gas buried underground — enough to supply the country for decades.
Not exact matches
In 2007, the Barnett
shale (Newark East) gas field produced 1.11 trillion cubic feet (31 billion cubic
metres)
of gas, making it the second - largest source
of natural gas in the United States.