GEOSCAN Search Results: Fastlink

GEOSCAN Menu


TitleEvidence for a deep gas-hydrate stability zone associated with submerged permafrost on the Canadian Arctic Beaufort Shelf, Northwest Territories
DownloadDownloads
AuthorRiedel, M; Taylor, G; Taylor, A E; Dallimore, S R
SourceGeological Survey of Canada, Current Research (Online) 2015-8, 2015, 21 pages, https://doi.org/10.4095/296987
Year2015
PublisherNatural Resources Canada
Documentserial
Lang.English
Mediadigital; on-line
File formatpdf
ProvinceNorthern offshore region
AreaBeaufort Sea; Beaufort Sea shelf; Beaufort Sea slope; Mackenzie Delta
Lat/Long WENS-138.0000 -134.0000 70.9667 69.9167
Subjectsgeophysics; fossil fuels; geophysical surveys; seismographs; seismological network; seismology; seismic waves; acoustic surveys; acoustic surveys, marine; bathymetry; continental shelf; continental slope; slope deposits; temperature; geothermal gradient; geothermal temperatures; permafrost; ground ice; hydrocarbons; hydrocarbon potential; gas; hydrate
ProgramMarine Geohazards, Public Safety Geoscience
Released2015 11 20
AbstractThe presence of offshore permafrost in the Canadian Beaufort Sea region has previously been identified from seismic and borehole data. The consequence of such permafrost is the possibility of an underlying gas-hydrate stability zone. In this study the authors present the first evidence for the widespread occurrence of gas hydrate in the offshore portion of the Beaufort Shelf using 3-D seismic data. A reflector of opposite polarity relative to the seafloor was identified at a depth of about 1000 m below seafloor that mimics some of the behaviour of the traditionally seen bottom-simulating reflectors in marine gas-hydrate regimes; however, the reflection identified is not truly bottom simulating, as its depth is rather controlled by the rapidly thinning wedge of submerged permafrost. The depth of the reflector decreases with increasing water depth, as predicted from thermal modelling. The reflection crosscuts strata and marks a zone of enhanced reflectivity underneath, possibly originating from free gas that accumulated at this phase boundary over time as the permafrost and associated gas-hydrate stability zones were thinning in response to the transgression. The presence of a clear and widespread gas-hydrate stability field beneath the permafrost has widespread implications on the region, including deep-drilling hazards associated with the presence of free gas, possible overpressure, and lateral migration of fluids and associated expulsion at the seafloor.
Summary(Plain Language Summary, not published)
The presence of offshore permafrost on the Canadian Beaufort Sea Shelf has long been recognized from seismic and borehole data. These thermal conditions could support a gas hydrate stability zone beneath the subsea permafrost. In this study we present the first evidence for the widespread occurrence of gas hydrate on the Beaufort Shelf using 3-D seismic data. A reflector was identified at a depth of ~1000 m that mimics some of the behaviour of the traditional bottom-simulating reflectors (BSRs) in marine gas hydrate regimes. However, the reflection is not truly bottom-simulating, as its depth is controlled by the thinning wedge of subsea permafrost. The reflection cross-cuts strata and marks a zone of enhanced reflectivity, possibly originating from free gas accumulated at this phase boundary. Implications of this widespread gas hydrate zone include: deep-drilling hazards associated with the free gas, potential overpressure, lateral fluid migration and associated seafloor expulsions.
GEOSCAN ID296987