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FROZEN HEAT
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Without Gas Hydrate
Porosity: 30-45%
Permeabilitiy 500-2000 md
Mechanical Strength: Low
With Gas Hydrate
Porosity: 10-15%
Permeability; 0.1 - 0.5 md
Gas Hydrate Saturation: 50-90%
100 microns
With Gas Hydrate
Porosity: 45-60%
Permeability: Nil (0.0001 md)
Gas Hydrate Saturation: 5-40%
Grain-displacing in disrupted, deformed sediments
(KG Basin, Ulleung Basin)
Silt and Sand-rich Host Sediments
Clay-rich Host Sediments
Without Gas Hydrate
Porosity: 50-70%
Permeability: Diminishes with Depth
to very low values (0.0001 md)
Mechanical Strength: Very Low
With Gas Hydrate
Porosity: 45-60%
Permeability: Nil (0.0001 md)
Gas Hydrate Saturation: 1-10%
Pore-filling in undisrupted sediments
(Blake Ridge)
100 microns
100 microns
Thinly interbedded
(Nankai Trough; Gulf of Mexico GC955)
Massively-bedded
(Gulf of MexicoWR313; Mallik)
Massive Occurrences (no host sediment)
Consolidated host sediments (rock)
(Messoyahki, Barrow (AK), Qilian Mtns (Tibet))
(Gulf of Mexico, Cascadia, others)
Variety of Lithologies
Porosity: Reduced due to grain
compaction, cementation
Permeabilitiy: Reduced 500-2000 md
Mechanical Strength: Very high
Figure 1.9:
Summary of how the host sediment controls the form of gas hydrate occurrence. Gas hydrates are primarily found in
unconsolidated sands (upper row) or clays (centre row). Hydrates also commonly occur in thin, hydrate-bearing sand layers separated by
fine-grained sediment (upper right), and can even form in sands that have themselves been consolidated, or packed more tightly together,
to form a rock (lower right). In clays, gas hydrates can exist in low concentrations in the small pores between grains (centre left). Gas
hydrates in higher concentrations tend to displace grains to form veins, lenses, and nodules (centre right), and those veins, lenses or
nodules can occasionally grow large enough to appear as a massive hydrate occurrences (lower left) (adapted from Boswell
et al.
2011).