Enormous quantities of bitumen are contained along the eastern margin of the Upper Devonian Grosmont Formation in northern Alberta. This formation can be readily subdivided into four informal stratigraphic units which represent, along with several smaller scale internal depositional cycles, successive stages in the evolution of a hugh carbonate complex: argillaceous slope sequences pass upward to a spectrum of shallow-platform facies and these then are capped by shoreline deposits and horizons of exposure and erosion. Although almost exclusively secondary in nature, the type and distribution of pore fabrics appear to have been at least initially controlled by original depositional facies.

In 1975, Union Oil Co. of Canada initiated a single well steam stimulation program to evaluate the potential for recovering bitumen from the upper Grosmont Formation. In 1977, the Alberta Oil Sands Technology and Research Authority (AOSTRA) and Canadian Superior Oil joined the project and further tests (steam stimulation, steam drive, combustion) were undertaken at a new site with Union continuing as operator. The 1980-81 "huff and puff" stimulation program consisted of one injection/production well and four closely spaced observation wells. Four production cycles have been completed to date, yielding attractively high production rates. An expanded evaluation program is currently under way and will utilize a five-spot scheme of injection/production wells augmented by four or more obse vation wells.

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