Postcards from the Edge: The Athabasca Oil Sands in Alberta, Canada, at It's Northeastern Limit

Hein, Frances J.¹, Darrell K. Cotterill², Mike Berhane³ (1) Alberta Energy and Utilities Board, Calgary, AB (2) Parallax Resources Ltd, Spruce Grove, AB (3) Alberta Energy and Utilities Board, Edmonton, AB

The Athabasca bitumen deposit is largely hosted in the Cretaceous McMurray Formation. Recent work focused at Lewis and Firebag-Sunrise along the eastern margin of the Bitumont Basin – a largely salt-withdrawal basin that sits above a potential graben. Regional stratigraphy of Lewis and Firebag-Sunrise, based on subsurface grids of 1807 wire-line logs and 100 cores, includes: Lower McMurray fluvial; Upper McMurray estuarine/coastal plain; Wabiskaw D valley-fill; Wabiskaw D regional marine shale; and Wabiskaw C marine. Further subdivision is McMurray A1 and A2 parasequences overlying channel complexes.

Individual facies percentages per core for karst breccia, slide/slump and debris-flow deposits, and overbank sediments of deltaic complexes are much more prevalent at Firebag-Sunrise compared to Lewis and to the Athabasca surface mineable area. Enhanced local thicknesses of these facies at Firebag-Sunrise reflects combined influences of regional salt dissolution and increased accommodation effects along the eastern margin of the Bitumont Basin during deposition of the McMurray units.

Paleogeographic evolution of the Lewis and Firebag-Sunrise areas includes: 1) pre-McMurray erosion and Lower McMurray fluvial lowstand; 2) Upper McMurray fluvio- transgression; 3) Upper McMurray A1 and A2 high-stand transgression; 4) Wabiskaw D maximum flooding of the main Wabiskaw-McMurray transgression; and 5) Wabiskaw C successions, formed during waning transgressive and initial regressive pulses. Detailed project analysis within the regional geological study identifies new prospective oil-sand deposits in eastern-sourced fluvial-deltaic complexes. Integration of the present project work with more regional geological studies of the Athabasca bitumen deposit allows for efficient development of these vast oil-sand resources of northeastern Alberta.