--> Abstract: Stratigraphic Architecture of the MacKay River Oil Sands Reservoir: Delineation of a Shoreface Shelf Tidal Sand Bar Complex Utilizing Sedimentological and Ichnological Trends, by Jenna M. Phillips, Mark Caplan, Murray Gingras, and George Pemberton; #90124 (2011)

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AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA

Stratigraphic Architecture of the MacKay River Oil Sands Reservoir: Delineation of a Shoreface Shelf Tidal Sand Bar Complex Utilizing Sedimentological and Ichnological Trends

Jenna M. Phillips1; Mark Caplan2; Murray Gingras1; George Pemberton1

(1) Earth and Atmospheric Science, University of Alberta, Edmonton, AB, Canada.

(2) Athabasca Oil Sands Corporation (AOSC), Calgary, AB, Canada.

The MacKay River oil sands reservoir is a SAGD project located in the west-central region of the Athabasca Oil Sands. The project area is characterized by a 20-40 m thick succession of lower Cretaceous McMurray-Wabiskaw strata that filled one of several clastic catchments entrenched into the underlying Devonian paleo-surface. The McMurray Formation comprises three to four superimposed northwest trending retrogradational to progradational shoreface shelf sands that erosionally truncate a thinly preserved package of estuarine deposits. These laterally continuous embayment-filling marine tidal sand bar complexes depart from the conventional, laterally heterogeneous fluvio-estuarine point bar sands observed in the main bitumen fairway.

Integrated sedimentologic, ichnologic, and stratigraphic data of cores and well logs has resulted in a depositional framework that comprises 7 facies associations (FA1-FA7). Ichnology and extensive facies mapping aided in delineating major sequence stratigraphic surfaces and distinct stratal packages. Estuarine deposits (FA1-FA2) consist of a low diversity, diminutive, mixed Skolithos-Cruziana ichnological suite dominated by Cylindrichnus, Gyrolithes and Teichichnus. Marine shoreface deposits (FA3-FA6) are characterized by linear sand bodies representing amalgamated proximal to distal tidal bars and rare highly burrowed interbar areas. These deposits illustrate higher diversities and larger marine traces of an overall proximal Cruziana ichnofacies.

The McMurray Formation accumulated in a secondary paleo-valley that formed an embayment west of the main valley system. Deposition was characterized by overall transgression and a starved sediment supply, resulting in overall retrogradation with episodes of progradation. Estuarine deposits occur at the base of the succession and represent the initial transgression and filling of the paleo-valley, where distribution was controlled largely by Devonian structure. Overlying deposits accumulated as tide-dominated to mixed wave-tide influenced delta front tidal sands and are separated from the underlying estuary by a tidal ravinement surface that developed during slow transgression. A transgressive surface of erosion demarcated by a Glossifungites surface and glauconite sands occurs near the top of the succession. The McMurray is bound by a maximum flooding surface characterized by offshore shales, followed by a gradational to sharp-based shoreface of the Wabiskaw Member (FA7).