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What are gas hydrates?
Gas hydrates or clathrates are crystalline compounds forming from water and gas
under certain P/T conditions. The title “clathrates” coming from Latin «clathratus»
which means “to put in a cage” was given by Pawll in 1948. These compounds are
non-stoichiometric that is they are of a variable composition.
Gas hydrates (of sulphur dioxide and chlorine gases) were observed for the first time
in the end of XVIII century by G. Pristly, B. Pelete and V. Karsten.
Water molecules form a framework (i.e. host lattice) with the cages.
These cages can be occupied with gas molecules (“guest” molecules).
Gas molecules are bonded with water molecules by Van der Waals forces.
Gas hydrates are described by general formula M*nH2O, where M is a molecule of
hydrate-forming gas, and n is the ratio that indicative the quantity of water
molecules to 1 molecule of gas (n varies from 5.75 to 17).
At present three crystal modifications of gas hydrates are known.
Structure I
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Structure II
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Structure H
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Gas hydrates form and exist under certain P/T conditions.The most of natural gases (CH4, C2H6,
C3H8, CO2, N2, H2S etc.) form hydrates.
Gas hydrates are globally widespread in nature, but concentrated in permafrost regions
and in oceanic continental margins. As far as known at presence, the most widespread
natural gas hydrate on Earth is mainly methane hydrate.
Phase P, T-diagram
of “water - methane” system
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The most of natural gases (CH4, C2H6,
C3H8, CO2, N2, H2S etc.) form hydrates.
Gas hydrates are globally widespread in nature, but concentrated in permafrost regions
and in oceanic continental margins. As far as known at presence, the most widespread
natural gas hydrate on Earth is mainly methane hydrate.
Because of its clathrate structure one volume of gas hydrate can contain
up to 160-180 m3 of pure gas.
Granting this gas hydrates are considered as a perspective energy resource.
| Burning of methane hydrate |
First industrial production of gas from hydrate
accumulations (Mallik, Mackenzie Delta, Canada) |
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Prospects of gas hydrates researches
 Gas hydrates as an alternative hydrocarbon resource
Development of gas in hydrate state transport technology
Technical problems solution during well-boring
and well exploiting in permafrost soils
Possibility of using gas hydrate accumulations
in permafrost zone for local gas supply
Development of technologies of hydrate formation
preventing in gas collection and industrial preparation systems
Development of technologies of gas fractionation
based on hydrate formation processes
Development of ŃÎ2 utilization
technologies based on ŃÎ2 transformation into hydrate state and subsequent
ŃÎ2 hydrate
disposal at sea bottom or in permafrost regions
Evaluation of methane and CO2
emission into atmosphere in case of global warming
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