FROZEN HEAT | Volume 1

General schematic showing typical modes of gas hydrate occurrence relative to the geologic environment

Relict Permafrost on recently inundated shelves (most climate sensitive?)

Permafrost

F

Pore-filling in sands at high concentration both within and below permafrost (some pre-existing free gas accumulations)

~350 to 600 m water depth (depending on bottom-water temperature)

Minimal Gas Hydrate (reduced gas supply) far offshore

Sea Floor Mounds

D

Hydrate at upper edge of stability (climate sensitive)

Sea Floor

Disseminated, pore-filling

Methane depleted zone

Hydrate-bearing sand

E

Hydrate-bearing Marine Clays Hydrate-bearing Deformed Clay

BIOGENIC GAS GENERATION

Water-bearing sand

A,B

C

200 to 1000 meters

Free gas

“Strata-bound” fractured muds

Deeply-buried, pore filling in sands (resource targets, climate buffered)

Gas Hydrate Stability Boundary

“Chimney Structures”: Dense fracture fills in muds

R. Boswell - 2011

THERMOGENIC GAS GENERATION AND MIGRATION

A

B

C

D

E

F

F

D

E

C

B

A

Figure 1.10: General schematic showing typical modes of gas hydrate occurrence relative to the geologic environment. Thin (A) and thickly veined (B) sediment-displacing gas hydrates (white) in fine-grained sediment (grey); (C) pore-filling gas hydrates in sand; (D) gas hydrate mounds on the sea floor (hydrate has an orange coating from oil and is draped with grey sediment); (E) disseminated gas hydrates (white specks) in fine-grained sediment (grey); (F) gas hydrates (white) in coarse sands (grey) (adapted from Boswell 2011).

FROZEN HEAT 26