A fuel buried under the deep ocean bed off Britain and Ireland could provide a plentiful supply of energy but will be difficult to exploit, an expert said.
The gas - known as fire ice - is locked away in the form of ice crystals under the Atlantic where the floor changes from shallow waters to deep sea.
But poor weather, the great distance from shore and technical challenges could make it hard to mine methane hydrate profitably.
Dr Chris Rochelle, a geo-chemist at the British Geological Survey, said: "It is exploitable, it is just going to be some way off-shore."
Existing reserves of oil, coal and gas have become tougher to access. Test wells have been drilled for shale gas in north west England.
In Northern Ireland environmental campaigners have railed against fracking exploration for the gas in Co Fermanagh.
Methane hydrate takes the form of crystals with natural methane gas locked inside. They are produced through a combination of low temperatures and high pressure and are found largely on the edge of continental shelves where the seabed drops sharply away into the deep ocean floor.
Mr Rochelle said the deposits were enormous.
"Estimates suggest that there is about the same amount of carbon in methane hydrates as there is in every other organic carbon store on the planet."
That means there is more energy in methane hydrates than in all the world's oil, coal and gas put together.
By lowering the pressure or raising the temperature, the hydrate breaks down into water and methane. One cubic metre of the compound releases about 160 cubic metres of gas, making it an energy-intensive fuel.
However with potentially easier access to shale gas, at this stage no serious plans are in place to retrieve methane hydrates from relatively near the UK, unlike research carried out in the US and Canada.
Mr Rochelle added: "We have to bring it back a long way, for other producers it is closer to shore.
"It is relatively deep water, it would be more challenging from the UK respect.
"That does not mean to say that companies from this part of the world could not take advantage of it by exploiting it in different parts of the world."