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The AAPG/Datapages Combined Publications Database

CSPG Bulletin

Abstract


Bulletin of Canadian Petroleum Geology
Vol. 38 (1990), No. 1. (March), Pages 160-160

C.S.P.G. 1990 Convention, "Basin Perspectives"

Hydrocarbon Generation and Previous HitMigrationNext Hit in the Western Canada Sedimentary Basin [Abstract]

Creaney, S.1, Allan, J.1, Previous HitFowlerNext Hit, M.2, Brooks, P.2, Macqueen, R.2

ABSTRACT

Multiple marine, oil-prone source rocks (at least ten) ranging in age from Middle Devonian to Late Cretaceous exist within the Western Canada Sedimentary Basin. Principle hydrocarbon reserves occur in the Lower Cretaceous Mannville Group and subcropping Paleozoic carbonates, where 270 times.gif (834 bytes) 109m3 (1.7 trillion barrels) of heavy oil form one of the largest deposits of oil on Earth. Biomarker analyses of these heavy oils, many conventional oils, and most source rocks in the basin, have been combined with basic geology to establish the source and Previous HitmigrationTop history of the Western Canada Sedimentary Basin.

Below the Joli Fou, several families of oils can be differentiated. Most of these are restricted geographically and/or stratigraphically, and can be easily related to specific source rocks. One group of conventional oils is more widespread and found in Lower Cretaceous Mannville and older, subcropping reservoirs. This group is related to the heavy oils, also found in subcropping Paleozoic and Mannville reservoirs. No single source has been unequivocally assigned to these hydrocarbons, and mixed sourcing is a possibility. Meteoric water incursion at the eastern limb of the basin permitted biodegradation, which converted the conventional Mannville crude oil to heavy oil (API gravities <25°). The Joli Fou shale and equivalents overlying the Mannville provide a regional seal for the Mannville and older strata. Oils present in the Viking, Cardium and Belly River sands are all from the one family, are sourced from the Colorado shale section, and are quite distinct from the oils in the Mannville and older section.

The Western Canada Sedimentary Basin also contains an estimated 5 times.gif (834 bytes) 1012m3 (180 TCF) of gas. Gas sources are marine, oil-prone source rocks where overmature, as well as Lower Cretaceous Mannville coals and coaly shales. Biogenic methane is also trapped on the eastern basin flank and includes the 3 TCF Medicine Hat pool. Hydrogen sulphide comes from overmature Paleozoic-Triassic evaporites/carbonates with an estimated 36 per cent of the total in-place gas reserves being classified as sour.

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ACKNOWLEDGMENTS AND ASSOCIATED FOOTNOTES

1 Esso Resources Canada Limited, Calgary T2P 0H6

2 Geological Survey of Canada, Calgary T2L 2A7

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