Integrated Stratigraphic Interpretation of the McMurray Formation SAGD Reservoir in Jackfish Area (Jackfish Phases 2 and 3), Alberta

Abstract

Devon's 1st commercial SAGD operation started with Jackfish phase 1 (JF1) in 2007 by producing bitumen from the Albian-Aptian McMurray Formation. In addition to operational excellence, the success of JF1 correlates very well with the high quality of the stacked fluvial reservoir sands targeted with horizontal well pairs. Although JF1 has excellent reservoir, reservoir quality does vary across the entire Jackfish acreage. Expansion to the west into phases 2 and 3 had to take into account a more complex reservoir heterogeneity and stratigraphic architecture. To characterize this more complex reservoir we used an integrated approach by combining 3D seismic, well logs, petrophysics, formation micro-imager images, interpreted dips, and core lithofacies to subdivide the McMurray into 3 main units informally termed MM-I, II and III from the bottom up. Unit MM-I is up to 5 m thick and is preserved as an erosional remnant resting unconformably on the Devonian. The main reservoir sands are within the MM-II unit, which ranges in thickness 40 to 50 m. Although seismic data quality is relatively poor over the JF area, seismic visualization has led to the identification of a fully preserved 300 m wide channel abandonment within MM-II. Further investigation by integrating core lithofacies, image logs and dipmeter from the 55 wells inside the abandonment suggests that this feature is part of a single fluvial point bar succession ∼35 m thick and 10 km² in area. Mapping the change in dip and azimuth of the inclined heterolithic facies in each well made it possible to reconstruct the scroll bar morphology and to understand the spatial distribution of sand versus mud within the point bar. This fluvial point bar unit overlies another succession that develops fully to the west where several fragments of point bars flanked by abandonment channels were mapped using a similar approach. We interpret MM-II as a succession of multiple vertically and laterally stacked meandering channel belts. The upper unit MM-III is relatively thin over the Jackfish phase 2 and 3 areas (0 to 15 m) and consists of several 2 to 5 m thick coarsening upward successions cut by 5 to 10 m thick sand-filled low sinuosity channels typical of a flood basin. The boundary between MM-II and MM-III is interpreted as a correlative flooding surface. Current understanding of stratigraphic architecture is being used to plan future delineation wells and orientate well pads for future bitumen development.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016