Methane hydrates, also called “flammable ice”, hold vast reserves of natural gas. China has for the first time extracted gas from the ice-like methane hydrate from under the South China Sea considered key to future global energy supply.
Many countries including the US and Japan are working on how to tap those reserves, but mining and extracting are extremely difficult.
It is believed that there is as much as 10 times the amount of gas in methane hydrates than in shale for instance.
The size of the oceanic methane clathrate reservoir is poorly known, and estimates of its size decreased by roughly an order of magnitude per decade since it was first recognized that clathrates could exist in the oceans during the 1960s and 1970.
Recent estimates constrained by direct sampling suggest the global inventory occupies between 1×10^15and 5×10^15 m³ (0.24 to 1.2 million cubic miles). This estimate, corresponding to 500–2500 gigatonnes carbon (Gt C), is smaller than the 5000 Gt C estimated for all other geo-organic fuel reserves but substantially larger than the ~230 Gt C estimated for other natural gas sources.