On the possible exploitation of methane hydrates from the seabed

The news

China has for the first time extracted gas from an ice-like substance under the South China Sea considered key to future global energy supply.
Chinese authorities have described success as a breakthrough.
Methane hydrates, also called "flammable ice", contain large reserves of natural gas.
http://www.bbc.com/news/world-asia-china-39971667

Basic data on methane hydrates.
Methane hydrates (methane clathrates) are extremely abundant on the seabed. Each solid liter of the hydrate contains 168 liters of methane at atmospheric pressure.
The nominal composition of methane clathrate hydrate is (CH4) 4 (H2O) 23, ie one mole of methane per 5.75 moles of water, corresponding to 13.4% methane. The actual composition depends on how many methane molecules fit into the structures of the water network. The most frequent density is around 0.9 g / cm3, for that reason the methane hydrate will float to the surface of the sea unless it is consolidated in a sedimentary plot that prevents him from ascending.
Therefore, one liter of fully saturated methane clathrate would contain approximately 120 grams of methane (or about 169 liters of methane gas at 0 ° C and 1 atm).
Naturally, methane hydrates occur in oceanic deposits on the continental shelf. They can also occur in deep sediment strata or near the sediment-water interface. They may be on the top of surging methane flows. According to the abiotic theory, the emanation of methane from depth is common in ocean bottoms, and therefore, the amounts of methane hydrates can be very large. There are also those who maintain that methane hydrates are formed by the action of organisms that live or are deposited on the seabed (biotic theory). Personally, I believe that there is increasing evidence of the deep origin of methane and the hydrocarbons derived from it. 
These deposits are located within an area of ​​average depth of about 300-500 m in sediment thickness where they coexist with the dissolved methane in fresh water of the pores of the sediments. Above this zone, methane is only present in its dissolved form at concentrations that decrease towards the surface of the sediment. Below it, the methane is gaseous. In the case of Blake Ridge on the continental shelf of the Atlantic Ocean, the stability zone of the methane hydrate began at 190 m depth and continued at 450 m where it reached equilibrium with the gas phase. Measurements indicated that methane occupied between 0 and 9% of the volume in the above-mentioned stability zone and 12% in the gaseous zone
Existing volumes of methane hydrates globally are estimated at several cubic kilometers (there are varying estimates but probably more (or more) of 5 km3 (5,000 million m3). According to these considerations methane hydrates could represent an important source of energy if they were exploited and hence the importance attached to this technological advancement of China.
Danilo Antón