Overlying the Precambrian basement, the sedimentary succession in the Wabamun Lake area has a maximum thickness of up to 3000 metres. It consists at its base of passive margin sediments, including evaporites, marine carbonates and shales from the Cambrian to Jurassic. The upper part is formed mainly by coarse to fine siliciclastics deposited in the Rocky Mountain foreland basin during the Cretaceous to present. Due to pre-Cretaceous erosion, Mississippian carbonates subcrop below Lower Cretaceous sandstones in the northeastern part of the study area. The sedimentary succession dips gently toward the southwest with a slope of 9 m/km. There are no known major faults in the area.
The details of the stratigraphy and lithology in the Wabamun Lake area are shown along a dip cross-section and a downhole lithostratigraphic model (Acrobat 7 PDF). Typically, sandstones and carbonates are aquifers, whereas shales and evaporites form aquitards. The sedimentary succession is subdivided by two thick aquitards, the Woodbend Group shales and the Colorado Group shales, into three main hydrostratigraphic groups:
Each major hydrostratigraphic group contains several aquifers and intervening aquitards. Some units also host hydrocarbon reservoirs and oil and gas production occurs mainly from the Banff Formation, the Lower Mannville Group, the Viking Formation, the Cardium Formation and the Basal Belly River Group.
For detailed basin information please see the Western Canada Sedimentary Basin Atlas. The geological map of Alberta is available online.
Three different pressure regimes govern the flow of formation fluids in the Wabamun Lake area. The lower part of the succession, from the Cambrian to the Lower Cretaceous Viking aquifer, is under pressured, with pressures ranging from 28 MPa at 3000 metres to 6.5 MPa at 1000 metre depth. Exceptions are over-pressured 'deep-basin style' hydrocarbon accumulations in the Lower Mannville and Cardium aquifers, which are hydrocarbon-saturated areas in the respective aquifer located downdip of the water leg. The shallow aquifers in the upper succession above the Colorado Group aquitard are normally to slightly sub-hydrostatically pressured, and formation water flow is driven by regional and local topography in the Wabamun Lake area. The salinity of formation water generally increases with depth, reaching 10 g/l in the Basal Belly River aquifer. All aquifers below the top of the Lea Park shales contain brines with salinity values above 20 g/l and up to 170 g/l in the Upper Devonian aquifers. No data exist for the Middle Devonian to Cambrian aquifers in the Wabamun Lake area, but regional-scale studies indicate salinity of formation waters of up to 300 g/l.
