ABSTRACT

The "Nordegg Member" of northwestern Alberta and northeastern B.C. (WCSB), is an organic-rich, highly radioactive, micritic limestone of Early Jurassic (Pliensbachian) age. This unit has been used as a marker horizon by petroleum personnel for many years. The petroleum potential of this unit, however, has largely been ignored. The organic and inorganic composition of the "Nordegg Member" are reported, in order to document the hydrocarbon potential of the "Nordegg", and the fate of hydrocarbons generated within this organic-rich unit. Analytical procedures employed in the study include Rock-Eval/TOC analysis, biomarker studies, organic petrographic techniques, and X-ray diffraction and scanning electron microscope with energy dispersive X-ray analysis.

Geochemical and geological data indicate that the deepest and most reducing conditions within the "Nordegg" basin (e.g., Pr/Ph <1.0, low clastic input, diasterane/regular sterane ratios <0.3) approximately coincide with a line joining T72, R24W5 and T84, R2W6. The "Nordegg" has excellent source rock characteristics (Type I/II kerogen, TOC's up to 28 per cent, large area in the "oil window"). However, comparison of the "Nordegg" biomarker signatures with those of oils trapped within the WCSB reveals that few conventional oils have been sourced by the "Nordegg". Also, the "Nordegg" does not appear to have been a major contributor to the Alberta heavy oil and tar sand deposits. We speculate that much of the oil generated by the "Nordegg" has not been expelled, and that this unit may be an important candidate for horizontal drilling plays.

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