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A GLOBAL OUTLOOK ON METHANE GAS HYDRATES
39
Figure 2.4-b:
Gas hydrates resource potential by global regions.
Estimates of the methane held in hydrates worldwide. Early
estimates for marine hydrates (encompassed by the green
region), made before hydrate had been recovered in the marine
environment, are high because they assume gas hydrates exist
in essentially all the world’s oceanic sediments. Subsequent
estimates are lower, but remain widely scattered (encompassed
by the blue region) because of continued uncertainty in the non-
uniform, heterogeneous distribution of organic carbon from which
the methane in hydrate is generated, as well as uncertainties in the
efficiency with which that methane is produced and then captured
in gas hydrate. Nonetheless, marine hydrates are expected to
contain one to two orders of magnitude more methane than exists
in natural gas reserves worldwide (brown square) (U.S. Energy
Information Administration 2010). Continental hydrate mass
estimates (encompassed by the pink region) tend to be about 1 per
cent of the marine estimates (Figure modified from Boswell and
Collett (2011)). Estimates are given in Gigatonnes of carbon (GtC)
for comparison with other organic hydrocarbon reservoirs. At
standard temperature and pressure, 1 GtC (Gigatonnes of carbon)
represents 1.9 Tcm (trillion cubic meters) of methane which has an
energy equivalent of approximately 74 EJ (exajoules).
the Gulf of Mexico (Frye
et al.
2008), and the eastern Nankai
Trough (Fujii
et al.
2008) provide insight into the resources that
might be available as sand-hosted gas hydrates. These studies
informed a recent global review by Johnson (2011), which pro-
vides a rough first-order estimate of the share of global in-place
resources of gas hydrates that could occur in sand reservoirs
(Figure 2.4). The estimate suggests significant potential tech-
nically recoverable resource (TRR) of gas hydrates in every re-
gion of the globe, with a cumulative mean estimate of in-place
resources within sand reservoirs of more than 1 217 trillion
cubic metres of gas. That value represents roughly 5 per cent of
the typical mid-range estimate for global gas hydrate in-place
resources. However, these estimates are highly speculative and
require significant field confirmation. The following sections
review a range of the best-studied occurrences of gas hydrates
in both coarse-grained and fine-grained reservoirs.
1
10
10
2
10
3
10
4
10
5
10
6
10
7
Global natural
gas reserves
(conventional)
First observation of marine hydrate
Estimates of the methane held
in hydrates worldwide
Gigatonnes carbon
1970 1975 1980 1985 1990 1995 2000 2005 2010
Methane in marine
gas hydrates
Methane in permafrost
gas hydrates
Methane in marine hydrates (based
only on the pressure and temperature
requirements for hydrate stability)
1
10
10
2
10
3
10
4
10
5
10
6
10
7
Global natural
gas reserves
(conventional)
First observation of marine hydrate
Estimates of the methane held
in hydrates orld ide
Gigatonnes carbon
1970 1975 1980 1985 1990 1995 2000 2005 2010
Methane in marine
gas hydrates
Methane in permafrost
gas hydrates
Methane in marine hydrates (based
only on the pressure and temperature
requirements for hydrate stability)