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TitlePermafrost investigation by well logs, and seismic velocity and repeated shallow temperature surveys, Beaufort-Mackenzie Basin
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AuthorHu, K; Issler, D R; Chen, Z; Brent, T A
SourceGeological Survey of Canada, Open File 6956, 2013, 33 pages, https://doi.org/10.4095/293120 (Open Access)
Year2013
PublisherNatural Resources Canada
Documentopen file
Lang.English
Mediaon-line; digital
File formatpdf
ProvinceYukon; Northwest Territories
NTS107; 117
AreaBeaufort-Mackenzie
Lat/Long WENS-142.0000 -128.0000 71.5000 68.0000
Subjectsgeophysics; surficial geology/geomorphology; pressure-temperature conditions; temperature; permafrost; freezing ground; ground ice; ground temperatures; formation fluids; pressure; resistivity logging; seismic velocities; geothermal gradient; seismic surveys; geophysical surveys; geophysical interpretations; resistivity logging; well log analyses; gamma ray logging; density logging; geophysical logging; Beaufort Mackenzie Basin
Illustrationslocation maps; tables; logs; stratigraphic columns; profiles; plots
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Location
 
Natural Resources Canada Library - Ottawa (Earth Sciences)
 
ProgramMackenzie Delta and Corridor, GEM: Geo-mapping for Energy and Minerals
Released2013 11 05
AbstractThis report presents exploration well data and interpretations relevant for mapping the variation in the depth to the base of ice-bearing permafrost (IBPF) for the Beaufort-Mackenzie Basin. This work is part of a larger government-industry funded petroleum systems study of the Beaufort-Mackenzie region that was active from 2001-2013. Geophysical well logs, well seismic surveys, shallow repeated temperature surveys, and deeper borehole temperature-depth profiles are utilized to determine the base of IBPF for 265 wells in the basin. Composite plots of log, seismic velocity and shallow temperature data illustrate typical geophysical responses and provide multi-parameter evidence for integrated interpretations of the IBPF zone. IBPF determinations are quality-assessed in terms of their reliability using a standardised scale based on the type of methods used and the quality of data available.
For many of the wells, a sharp change in electrical and acoustic properties marks the base of the interpreted fully frozen IBPF zone which may represent the base of ice-bonded permafrost. For 135 wells, there is an underlying transition zone between 7 m to 210 m in thickness that is interpreted to represent partially-frozen IBPF. The interpreted co-existence of water and ice may be the result of changes in lithology, grain size, texture and/or pore water salinity which can affect the freezing point. There is a good correlation between the geophysically-determined base of IBPF and the depth to the base of permafrost from temperature surveys. This suggests that the mapped IBPF zone is a useful thermal boundary condition for thermal modelling and heat flow studies.
For most of the wells, IBPF is confined to sandstones and conglomerates within Cenozoic sediments of the post-rift succession. Beneath the Beaufort Shelf, base of IBPF occurs within highly porous sediments of the Plio-Pleistocene Iperk Sequence. For central onshore areas (Richards Island and areas to south), base of IBPF occurs in progressively older, more deeply exhumed Cenozoic strata in a southward direction. Along the southeastern basin margin on Tuktoyaktuk Peninsula, IBPF extends into the Paleocene-Eocene Aklak Sequence. In the southernmost part of the basin and in the fold belt to the west, IBPF is encountered in Lower Cretaceous syn-rift and Upper Cretaceous post-rift strata. Permafrost occurs in exhumed Paleozoic strata in the Anderson Plain southwest of Tuktoyaktuk Peninsula. Depth to the base of IBPF varies from 0 m (no IBPF) to > 700 m across the study area. It is thinnest along the southern (landward) basin margin and in the deformed and exhumed western part of the basin, and is thickest in the rapidly deposited Cenozoic strata of the eastern shelf beneath the Beaufort Sea. IBPF may be absent over much of the modern delta area around Mackenzie Bay.
Summary(Plain Language Summary, not published)
This report provides detailed exploration well data, techniques and interpretations of permafrost determinations for the Beaufort-Mackenzie Basin. Geophysical well logs, well seismic surveys, shallow repeated temperature surveys, and deeper borehole temperature-depth profiles are utilized to determine the base of ice-bearing permafrost (IBPF) for 265 wells. An integrated, multi-parameter approach to permafrost characterisation is presented and quality assessment procedures are discussed. Determined base of IBPF varies from 0 m (no IBPF) to > 700 m across the study area. Sharp changes in electrical and acoustic properties can mark the base of the interpreted fully frozen IBPF zone. An underlying transition zone may exist (7~210 m in thickness) interpreted to represent a partially-frozen IBPF zone observed in 135 wells. An excellent correlation between geophysically-determined base of IBPF and the base of permafrost from shallow temperature surveys suggests that borehole geophysical methods reliably predict permafrost distribution
GEOSCAN ID293120