The "Energy Crisis" is over, according to some analyses, with new gas discoveries securing supplies for as much as 250 years.
Conventional gas reserves peaked in 1970, which made the "dash for gas" in the late 1980s, with gas replacing oil and coal for power generation, seem particularly short-sighted at the time. The UK led the trend, but gas production from North Sea fields has been falling steadily.
In 2002 the Royal Academy of Engineering predicted blackouts within two years, as supplies dwindled.
The dash for gas doesn't seem quite so short-sighted now.
The US Energy Information Administration takes a conservative view, estimating that reserves are 40 per cent larger than previously thought, if shale is included. The figure for technically recoverable reserves is now six times greater than the proven reserves.
The big winners include Argentina with 774 trillion cubic feet, South Africa, with 485, Poland, with 187, France with 180, and the North Americas. Canada (385) the USA (862) and Mexico (681) have vast reserves. China (1,275) has the largest. Australia's domestic energy production will benefit from 396 trillion cubic feet of technically recoverable reserves.
By comparison, North Sea reserves are around 20 trillion cubic feet. The UK's consumption in 2009 was 3.11 tcf.
According to the EIA, the US has anyway 50 years' gas supplies. The UK could return to self-sufficiency in gas at least in the shorter term,
Not all producers were surveyed - Russia, for example, Central Africa or the Middle East.
Shale or 'deep gas' is excavated using two techniques, fracturing or "fracking", and horizontal drilling, to find gas several thousand feet lower than using conventional sources.
UK exploration is taking place near Blackpool, with the Cuadrilla consortium expected to report its results in July. It's already said the shale seam is much thicker than estimated by the Royal Geological Society. ®