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 Yuill^2
1 Total, formerly seconded to Conocophillips Canada, Pau, France
² ConocoPhillips Canada, Calgary

The bitumen sands of the McMurray outcrop 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 Fm 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 significant erosions. 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 further south as amalgamation and erosion rates are significantly stronger due to a more proximal fluvial setting.

AAPG Search and Discovery Article #90039©2005 AAPG Calgary, Alberta, June 16-19, 2005