Introduction The Grosmont Formation is an Upper Devonian carbonate succession that is present in northeastern Alberta. It contains 318 billion barrels of bitumen on the basis of Alberta government estimates (Alberta Energy Resources Conservation Board, 1996). Figure 1 is a map of the interpreted bitumen resource on the basis of Energy Resources Conservation Board mapping. This map also shows the location of Laricina Energy’s Saleski land block in the heart of the bitumen accumulation. During the winters of 2006–2007 and 2007–2008, Laricina Energy drilled 21 vertical wells for the purposes of bitumen resource delineation. In addition, one horizontal well was drilled as part of a proposed steam-assisted gravity drainage (SAGD) pilot. The Grosmont Formation is a 120-m thick carbonate succession that is sandwiched between shales of the Upper and Lower Ireton Formation within the Woodbend Group. It has been subdivided chronologically into the A, B, C, and D units. These subdivisions correspond to Cutler’s (1983) units LG, G1, G2, and G3, respectively. The lowermost three units were deposited during shallowing-upward depositional cycles. The uppermost unit, the Grosmont D, is an aggradational depositional unit. Grosmont strata dip gently to the southwest. The Grosmont has been bevelled by erosion in an easterly direction.

Abstract This sequence comprises the strata between the Beaverhill Lake Group (Chapter 7) and the Winterburn Group (Chapter 9). The stratigraphic section includes shallow-water carbonates of the Cooking Lake, Leduc and Grosmont formations and deep-water carbonates and shales of the Majeau Lake Member, Duvernay and Ireton formations. The isolate reef complexes of the Leduc Formation are especially well known because they contain some of the largest oil reserves in the WCSB. In central Alberta, the basin-fill succession of the Woodbend Group differs markedly from that of the underlying Beaverhill Lake Group. Rather than being comprised dominantly of carbonate muds derived from coeval carbonate banks to the east, Woodbend basin-fill units have a significant clay shale content. The occurrence of these shales marks the initial delivery of terrigenous deposits into the central Alberta Basin from an extrabasinal northerly source. The configuration of these shale "banks" controls the distribution of some overlying carbonate platform deposits. Figure 1 depicts the configuration of the Alberta Basin during the Woodbend which marks the furthest incursion of the open-marine Devonian seaway onto the craton. Shallow-water platform carbonates occur along the periphery of this basin in east-central Alberta, in the Devonian "Deep Basin" area of west-central Alberta and around the Peace River Arch landmass.