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TitleEvidence for deep anaerobic biodegredation associated with rapid sedimentation and burial in the Beaufort-Mackenzie basin, Canada
AuthorGrasby, S E; Chen, Z; Issler, D; Stasiuk, L
SourceApplied Geochemistry vol. 24, 2009 p. 536-542,
Alt SeriesEarth Sciences Sector, Contribution Series 20080088
PublisherElsevier BV
Mediapaper; on-line; digital
File formatpdf
ProvinceNorthern offshore region; Northwest Territories
NTS107B; 107C; 107D/12; 107D/13; 107D/14; 107E/02; 107E/03; 107E/04
AreaBeaufort-Mackenzie Basin; Beaufort Sea; Mackenzie Delta; Tuktoyaktuk Peninsula
Lat/Long WENS-138.0000 -129.0000 71.0000 68.0000
Subjectssedimentology; fossil fuels; geochemistry; hydrogeology; sedimentation; depositional environment; formation water; water analyses; carbon dioxide; water geochemistry; salinity; alkalinity; geological history; groundwater regimes; Cenozoic; Mesozoic; Cretaceous
Illustrationslocation maps; stratigraphic columns; histograms; plots; cross-sections
ProgramSecure Canadian Energy Supply
AbstractFormation waters of the 14 km thick late Cretaceous - Cenozoic Beaufort - Mackenzie basin were examined as part of a larger project to better understand the petroleum potential of the region, where early exploration defined petroleum reserves of 744 x 10 9 bbls recoverable crude oil and 11.74 tcf gas. Historical water analyses (2583 samples from 250 wells drilled up to 5 km depth) were compiled and culled to remove incomplete and poor quality samples. The resultant database shows a broad range of salinity and water chemistry that has no systematic relationship with depth. Three main water types are defined, paleo seawater, and freshwaters related to a Miocene age gravity-driven flow system, and low TDS - high alkalinity waters. High alkalinity waters are isolated in overpressured fault blocks that were rapidly buried by post-Miocene Iperk shale deposition. The high alkalinities (up to 9000 mg/L) are interpreted to be related to in situ CO2 generation through anaerobic methanogenesis in response to freshwater invasion. The dominant control on biogenic gas generation appears to be maximum burial temperature rather than the modern temperature distribution. This is consistent with the paleopasteurization model that suggests once critical burial temperatures are reached, sterilized rocks are inhibited from further biodegradation, even when temperatures subsequently drop back into the habitable zone.