ABSTRACT

The Upper Mississippian Kiskatinaw Formation is an important sandstone reservoir in the Peace River region of northwestern Alberta and northeastern British Columbia. It exhibits complicated stratigraphy, sedimentology, and structure largely due to its location on the Peace River Arch. The primary gas reservoirs in the Kiskatinaw are basal channel sandstones up to 30 m thick, which have fluvial, estuarine, and tidal characteristics.

Porosity and permeability in the Kiskatinaw decrease substantially downdip from the subcrop edge. Thin section petrography of the producing basal sand near the erosional edge (Balsam and Josephine fields) indicates that diagenesis has played an important role in porosity preservation and creation. The quartzose sands are cemented with varying quantities of quartz overgrowths, dolomite, and anhydrite. Diagenetic textures indicate substantial porosity enhancement through dissolution of anhydrite, dolomite, and quartz. Microporous dolomite is very abundant and commonly occurs in oversized pores, which in some places contain ghosts of pre-existing grains, such as pellets. Microporosity has also been created by alteration of potassium feldspars to kaolinite, and of kaolinite to chlorite. Corroded chert, glauconite, pellets, ooids, and shale grains are present locally. Kaolinite, chlorite, and siderite occur as pore-filling and pore-lining authigenic minerals. Chlorite also occurs as replacement of pellets and shale clasts.

Enhanced porosity may be a product of greater contact at the unconformity surface with fluids, possibly less saline than evaporitic waters. Fluid flow may have been facilitated by faulting and the major unconformity truncating the Kiskatinaw.

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