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Geology of Syncrude Oil-Sand Leases

Adel O. Tammam, Grant D. Wach

The role of geology in oil-sand exploration was initially limited to the economic inventory of the resources. Only recently has the knowledge of the intricate distribution of the lithology and related environments of deposition become important, since the day-to-day handling of feed material of variable lithology and bitumen quality has caused operational problems and differences between expected and actual performance of mining and extraction equipment.

The detailed mapping, by several geologists, of the Lower Cretaceous McMurray Formation within the Syncrude leases, supplemented by outcrop mapping, formed the basis for classifying the rock units. This classification was used to develop a practical depositional model to assist in planning exploration strategies.

The basic depositional framework of the McMurray Formation within the Syncrude leases has been established as that of an overall transgressive sequence. The early sediments consisted of pond, overbank, and crevasse splay with point-bar deposits in a fluvial or flood-plain environment.

The approach of the Clearwater Sea established a tidally influenced estuarine environment with an extensive network of channels and flats. This allowed the deposition of a variety of sediments, including channel sands, channel breccia, and bedded and bioturbated muddy and sandy tidal-flat deposits. The system was eventually inundated by the encroaching sea, which deposited various sediments represented by lagoonal muds, nearshore shoal and shoreface sands, and shelf marine muds.

The upper contact of the McMurray Formation is transitional into the overlying Lower Cretaceous Clearwater Formation and is marked by the glauconitic shelf sands of the Wabiskaw Member.

AAPG Search and Discovery Article #91043©1986 AAPG Annual Convention, Atlanta, Georgia, June 15-18, 1986.