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GEOREF RECORD

Late Laramide dolomite recrystallization of the Husky Rainbow "A" hydrocarbon Devonian reservoir, northwestern Alberta, Canada; paleomagnetic and geochemical evidence

Michael T. Lewchuk, Ihsan S. Al-Aasm, David T. A. Symons and Kevin P. Gillen
Late Laramide dolomite recrystallization of the Husky Rainbow "A" hydrocarbon Devonian reservoir, northwestern Alberta, Canada; paleomagnetic and geochemical evidence
Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre (January 2000) 37 (1): 17-29

Abstract

The Rainbow Field is in reefal carbonates of the Middle Devonian Keg River Formation in the Western Canada Sedimentary Basin. Alternating field and thermal step demagnetization was done on specimens from unoriented core from a vertical, an inclined, and a horizontal well core in the dolomite reservoir. Although they had no viscous remanent magnetization component to use for orientation, most specimens had a well-defined characteristic remanent magnetization (ChRM) that resides in single to pseudosingle domain magnetite. By rotating the mean ChRM direction around its core axis, a small circle can be generated for each core and the small circles intersect in the true ChRM direction of D = 168 degrees , I = -73.5 degrees (alpha (sub 95) = 5.8 degrees , k = 32.2). Its paleopole of 164 degrees E, 83 degrees N (A (sub 95) = 10 degrees ) defines a Tertiary age with one sigma limits of Middle Eocene to Middle Miocene age. Petrographic examination defines four generations of dolomite. Matrix dolomite has 60-100 mu m diameter crystals that were later recrystallized to 200-400 mu m. Dolomite cements are represented by vug-filling coarse dolomite (100-200 mu m) and saddle dolomite (1000 mu m). All four generations of dolomite give similar delta (super 18) O values of -10.7 to -16.5 per mil (Peedee Belemnite, PDB), delta (super 13) C values of +0.7 to +3.2 per mil (PDB), and Sr isotopic ratios of 0.70826 to 0.70846 that do not match the expected Middle Devonian carbonate or seawater values. We interpret these data to indicate that mixed pre-Laramide basinal fluids, heated by burial during the Laramide Orogeny, were present during late Laramide time when the dolomites were recrystallized and (or) precipitated prior to petroleum migration and accumulation in the Rainbow "A" reservoir. Thus the combined use of paleomagnetism, geochemistry, and petrography has been proven to be a useful technique to date and identify dolomitization events and pathways for the migration of hydrocarbons.


ISSN: 0008-4077
EISSN: 1480-3313
Coden: CJESAP
Serial Title: Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre
Serial Volume: 37
Serial Issue: 1
Title: Late Laramide dolomite recrystallization of the Husky Rainbow "A" hydrocarbon Devonian reservoir, northwestern Alberta, Canada; paleomagnetic and geochemical evidence
Affiliation: University of Oklahoma, School of Geology and Geophysics, Norman, OK, United States
Pages: 17-29
Published: 200001
Text Language: English
Summary Language: French
Publisher: National Research Council of Canada, Ottawa, ON, Canada
References: 55
Accession Number: 2000-041945
Categories: Economic geology, geology of energy sourcesIsotope geochemistry
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 2 tables, sketch maps
N58°19'60" - N58°40'00", W119°25'00" - W119°15'00"
Secondary Affiliation: University of Windsor, CAN, CanadaVox Terrae International, CAN, Canada
Country of Publication: Canada
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute.
Update Code: 200014
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