The Suffield heavy oil sands are found in the glauconitic sandstone of the Mannville Group in two major north-south-trending sand belts ranging in thickness from 15 to 20 m. The study area is centered around a heavy oil pilot site which is a joint venture operated by Alberta Energy Co., Alberta Oil Sands Technology and Research Authority, Dome Petroleum, and Westcoast Petroleum. At this location, the glauconitic sandstone is a 46-m thick, uninterrupted sandstone partly saturated with 13° API oil. The sandstone geometry, and the sequence of lithologies and sedimentary structures, indicate deposition in a prograding shoreline beach environment. An upward transition of facies from lower and middle shoreface sands, through foreshore, to backshore, marsh, and continental eposits, is represented. The sandstone is composed of quartz, chert, sedimentary rock fragments, trace amounts of feldspar, and 2 to 30 wt. % clay. Kaolinite, the dominant clay mineral, occurs as (1) small platelets forming grain linings and pore bridges, (2) vermicular growths, and (3) silt-sized rock fragments. Lesser amounts of illite, smectite, and mixed-layer clays occur as ridges on grain surfaces and as pore bridges. Illite can also occur as needlelike projections. The most argillaceous sands, located at the top of the sandstone unit, contain only very fine-grained kaolinite. Quartz overgrowths contribute to porosity reduction in the cleaner sands. Minor amounts of secondary porosity can be identified by the presence of partly leached feldspar grains.

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