Presentation 2016-009

Author(s) Date 2016-06-21

In the Athabasca Oil Sands area, the basal Wabiskaw Member of the Clearwater Formation includes the upper part of the Wabiskaw-McMurray oil sands deposit, and overlying Clearwater Formation marine shale forms the cap rock to that reservoir. Farther south, Clearwater Formation strata overlying the Wabiskaw Member form the primary bitumen reservoir in the Cold Lake Oil Sands area. The regional-scale delineation and modelling of bounding lithostratigraphic surfaces and key internal subdivisions of the Clearwater Formation form an important component of a wider Alberta Geological Survey project to construct a digital 3D geological model for the Lower Athabasca Regional Plan area in northeast Alberta using available wireline log data. The regionally applicable stratigraphic scheme of E surfaces (erosional surfaces with pronounced relief) and T surfaces (transgressive/flooding surfaces with low relief), developed during Alberta Geological Survey mapping of the Athabasca Oil Sands area north of Township 67 from 1986 onward, has been extended south into the Cold Lake area. Building on preliminary work by Hein et al. (2007), this new work allows mapping of incised valley-fill complexes in the upper Wabiskaw Member and overlying undifferentiated Clearwater Formation. E surfaces at the bases of these intervals truncate older Clearwater Formation strata and locally, the underlying McMurray Formation. With this stratigraphic framework in place, detailed project-scale studies of this complex basal Clearwater interval can be placed in a wider regional context. The top of the Clearwater Formation is placed at the basal contacts of successive northwestward offlapping Grand Rapids Formation sand bodies. This time-transgressive lithostratigraphic contact has been mapped as a composite surface that steps up-section from the base of the sandstone overlying the mudstone interval immediately above the T31 transgressive surface in the Cold Lake area (consistent with industry practice in that area), to the base of the Grand Rapids Formation Alice Creek Tongue sandstone at the northwest limit of the study area in the Birch Mountains. Development of a regional-scale stratigraphic model for the Clearwater Formation in northeast Alberta represents a key step towards increased understanding of this important reservoir and cap-rock interval.

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American Association of Petroleum Geologists - ACE 2016