The importance of natural gas hydrates as a potential fossil fuel is a subject of much current interest.
However, it is still impossible to unambiguously answer the question "Economic use of hydrates: dream or reality?". We lack sufficient knowledge and the required stage of research work has not been accomplished yet.
Most of the gas hydrate occurrences in the World Ocean (42 of 64) has emerged from indirect features, mainly from observations of the Bottom Simulating Reflector (BSR). The nature of BSR cannot be indicative of particular gas hydrate accumulations but only justify the gas hydrate prone areas.
The available global estimates of gas amount in natural gas hydrates differ by more than four orders of magnitude (1.8·1014 to 7.6·1018 m3). Most of the published estimates are overestimated, because they are based on a paradigm formed at the early stage of research and it states that submarine gas hydrates are marked by a continuous distribution over large areas and at a wide range of subbottom depths and by a high hydrate content of deposits. These considerations do not comply with observational data, namely, has hydrates show discrete occurrence as isolate accumulations. The estimates 1.8·1014 to 1·1015 m3 seem to be most realistic.
In future gas hydrate accumulations related to fluid discharge areas will probably be more feasible resource. Such accumulations occur on the immediate sea floor and they are marked by a relatively high hydrate content of deposits. Therefore, we have all the ground to suggest that gas resources in hydrates of these accumulations are renewable.
The first reliable discovery of gas hydrates took place less than a quarter of a century ago: they were reported and described from the Black Sea in 19741 and Caspian Sea in 19792. The intense study of natural gas hydrates especially during the last decade was caused by several reasons. Gas hydrates are considered as a potential fossil fuel; as a source atmospheric emission of greenhouse gas; as a factor affecting instability of continental and island slopes; as an environment component complicating the economic activity during the development of the offshore natural resources.
Globally, the interest to natural gas hydrates as a possible energy source capable to deficit of hydrocarbons in the future was stirred up primarily by a huge amount of gas in hydrates mentioned in numerous published estimates. However, the estimates differ by several orders of magnitude implying uncertainty concerning the real extent of gas hydrates in the earth interior, primarily submarine. All the other issues related to natural gas hydrates are considered to be secondary to the above mentioned.
The paper 1) provides an overview and analysis of observations of gas hydrates and their features