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Table 3.1-a:
Production challenges and associated environmental considerations for permafrost gas hydrate deposits
1. Likely commerciality time-line (i.e., produceable/non-produceable in the near future)
Reservoir type
Onshore –
Sand-host
sediment
Onshore –
Other host
sediment
environments
Offshore –
Variable host
sediment
environments
Environmental response
– Negligible ground surface
interactions are expected as
the most prospective gas
hydrate accumulations are
buried many hundreds of
metres below the ground
level, beneath a competent
permafrost interval
– Control on reaction
provided by ability to control
pressure in the well bore.
– Seal integrity expected
to be sufficient as the
accumulations are likely to
be converted, pre-existing,
free gas traps.
Not considered
Not considered
Not considered
Drilling, completion & production
– Conventional drilling practice
& sand control/flow assurance
measures
– Dissociation primarily through
pressure draw-down (down-hole
pump)
– Challenges associated with
low reservoir temperatures &
retaining formation integrity
when hydrates are dissociating
– Subsurface water-disposal
strategy will be required
– Flow assurance measures will
be necessary to reduce risk of
secondary gas hydrate formation
in gas production stream
– Horizontal wells may be required
Not considered
Not considered
Not considered
Site survey & foundation considerations
– Several well described sites have
been identified in North America
– Environmental and geo-hazard
issues related to near surface
infrastructure expected to be similar
to conventional
Not considered
Not considered
Not considered
Production maturity
1
– Discovered technically
recoverable resources
(Alaska North Slope and
Arctic Canada)
– With completion of
demonstration projects at
Mallik site in Mackenzie
Delta, currently existing
production technologies
have been verified. However,
market and infrastructure not
presently in place.
– No technically recoverable
resources identified (Seismic
evaluation complex due to
hydrate-ice similarities)
– Development hindered by
low reservoir temperatures
– No technically recoverable
resources identified
– Gas hydrate saturation
and reservoir extent unclear,
additional work needed
– No technically recoverable
resources identified
– Gas hydrate saturation
and reservoir extent unclear,
additional work needed
Reservoir setting
Beneath permafrost
– Pore-space occurrence
– Temp. 0 to ~12 °C
– Sites: Alaska North Slope
(USA), Mackenzie-Beaufort/
Arctic Islands(Canada) and
Siberia (Russia)
Within permafrost
– Pore-space occurrence
– Temp. < 0 °C
– Sites: as above
Within and beneath
permafrost
– pore and fracture fill
modes in fine grained strata,
lithified sediments with low
permeability etc.
– Sites: Qilian Mtns,
China; also likely in other
permafrost settings but
presently not documented
Thick offshore permafrost
occurrences are suspected
beneath the Arctic shelves
(Beaufort Sea, Siberia) where
terrestrially formed deposits
have been submerged by
transgression. Gas hydrate
can be expected within
and beneath permafrost in
settings similar to those
described above