http://marine.usgs.gov/fact-sheets/gas-hydrates/ <– No longer works
They are several years old.
The same day I settled in to read the Times and came across Matt Ridley’s long piece on…Gas hydrates!
The world will use about 450 exajoules (billion billion joules) of fossil fuel energy this year and has so far used less than 20,000 exajoules since the Industrial Revolution began. Total oil, gas and coal resources in the Earth’s crust are estimated at more than 570,000 exajoules. So if energy use was a journey from St Pancras to Istanbul by train, we have not yet reached the Channel Tunnel. Resources can be finite yet effectively inexhaustible or, like dodos and forests, infinitely renewable yet easily exhausted.
Quantity is not really the point; price is. Most fossil fuels are impossibly hard to extract at a reasonable price. More than half the reserves consist of methane clathrates hydrated gas found mostly on the seabed near the margins of the continents in vast quantities. Nobody knows how to turn them into fuel except at huge cost, although the Japanese are on the case. So the question is not whether we run out of fossil fuels but whether we run out of cheap fossil fuels.
Read it, its part of his Rational Optimist series, and very good.