The Bitumen-Bearing McMurray Formation: Description of Reservoir Units in a Large Fluvio-Estuarine Setting from the Athabasca and Christina Rivers Outcrops, Alberta, Canada*

Alain Lejay¹ and Catherine Yuill²

Search and Discovery Article #10092 (2005)

Posted September 18, 2005

*Oral presentation at AAPG Annual Convention, Calgary, Alberta, June 19-22, 2005

Click to view presentation in PDF format.

¹Total, Pau, France ([email protected]) (formerly seconded to ConocoPhillips Canada)

²ConocoPhillips Canada, Calgary ([email protected])

Abstract

The bitumen sands of the McMurray crop out extensively in the Ft. McMurray area and have provided a tremendous opportunity for a detailed study of the facies and geometry of the reservoir units found in subsurface in the vicinity. Photo-panoramas supplemented by detailed sedimentary logs and also by field GR measurements were built. The global architecture of the McMurray Formation is directly influenced by an overall transgressive trend. A basal unit is characterized by fluvio-deltaic facies, including coarse-grained Gilbert deltas. A prominent intermediate unit is characterized by large-scale meandering fluvio-distributary channels that form the known Heterolithic Stratifications. The sedimentary facies, dominated by climbing ripples, show that the tidal activity had a minimal impact on the deposition and suggest that these channels are more fluvial than tidal-dominated. Episodic fluvial flood events are commonly observed and generate numerous occurrences of significant erosion. The last sequences of the McMurray record a marked marine influence with thinner and shalier channels, some being almost entirely bioturbated and interpreted as distributary-lagoonal meandering channels. The sedimentary model from these outcrops can be extrapolated to the surrounding bitumen fields. However, we should be cautious to make comparisons with fields located farther south, as amalgamation and erosion rates are significantly stronger due to a more proximal fluvial setting.