Minerals Report - International Seabed Authority

The present mapping of worldwide distribution of methane
hydrate zones is far from adequate and the techniques for proper
quantification of the volume of methane in these zones is yet to be
developed. In this situation, the amount of methane in hydrates estimated
by various workers is highly variable (Table 2).
Table 2. Estimates of the amount of methane in gas hydrates prepared by
Potential Gas Committee (Adapted after Kvenvolden*)
Cubic metres
Oceanic:
Trillion
feet
cubic
3.1 x 1015 (5-25) x 1015 7.6 x 1018 Continental:
1.4 x 10 13
3.1 x 10 13
5.7 x 10 13
3.4 x 10 16
1.1 x 10 5
(1.8-8.8) x 10 5
2.7 x 10 8
5.0 x 10 2
1.1 x 10 3
2.0 x 10 3
1.2 x 10 6
Gigatons References
1.7 x 10 3
(2.7-13.7) x 10 3
4.1 x 10 6
0.75 x 10 1
1.7 x 10 1
3.1 x 10 1
1.8 x 10 4
McIver 17
Trofimuk et al 18
Dobrynin et. al. 19
Meyer 20
McIver 17
Trofimuk et. al. 18
Dobrynin et. al. 19
However, it is considered that about 10,000 Gigaton is a reasonable
estimate of carbon stored in methane hydrates 12 . This quantum of organic
carbon in gas hydrates is twice that in all known fossil-fuel deposits. Even
if only a small percentage of this is recover- able, it will constitute a major
stock of energy.
3. Formation of Methane Hydrate in Sediment
3.1. Generation of Methane in sediments
Sub-seabed methane within the continental margin sediments is
produced primarily by microbial and thermogenic processes.
In the microbial process the organic debris of the depositing
sediments are decomposed by a complex sequence (methanogenesis) into
INTERNATIONAL SEABED AUTHORITY 523