The estimated amount of gas
in the hydrate accumulations of the world greatly exceeds the volume
of known conventional gas reserves. However, the role that gas hydrates
will play in contributing to the world’s energy requirements will depend
ultimately on the availability of sufficient gas hydrate resources and
the “cost” to extract them. Yet considerable uncertainty and disagreement
prevails concerning the world’s gas hydrate resources.
Gas hydrates occur in sedimentary
deposits under conditions of pressure and temperature present in permafrost
regions and beneath the sea in outer continental margins. The combined
information from Arctic gas-hydrate studies shows that, in permafrost
regions, gas hydrates may exist at subsurface depths ranging from about
130 to 2,000 m. The presence of gas hydrates in offshore continental
margins has been inferred mainly from anomalous seismic reflectors known
as bottom-simulating reflectors, that have been mapped at depths below
the sea floor ranging from about 100 to 1,100 m. Current estimates
of the amount of gas in the world’s marine and permafrost gas hydrate
accumulations are in rough accord at about 20,000 trillion cubic meters.
Gas hydrate as an energy
commodity is often grouped with other unconventional hydrocarbon resources.
In most cases, the evolution of a non-producible unconventional resource
to a producible energy resource has relied on significant capital investment
and technology development. To evaluate the energy resource potential
of gas hydrates, will also require the support of sustained research
and development programs.
Despite the fact that relatively
little is known about the ultimate resource potential of natural gas
hydrates, it is certain that gas hydrates are a vast storehouse of natural
gas and significant technical challenges need to be met before this
enormous resource can be considered an economically producible reserve.