Local-Scale Baseline Subsurface Hydrogeology at the AOSTRA Underground Test Facility

This report presents the baseline hydrostratigraphy, hydrogeology and aquifer properties in the Phanerozoic sedimentary succession in an area of approximately 500 km² (2x3 townships) surrounding the Alberta Oil Sands Technology and Research Authority (AOSTRA) Underground Test Facility (UTF) near Fort McMurray in northeast Alberta. The study was prompted by AOSTRA's plans to expand the Underground Test Facility to a pilot operation. As part of this expansion, it is envisaged to dispose of residual waters by on-site deep well injection. Environment Canada and the Alberta Research Council initiated in 1990 a collaborative study on the effects of deep injection of residual water at the UTF site, with data support and cooperation from AOSTRA. The evaluation of the effects of deep injection of residual water is based on predictive modeling, which requires knowledge of the initial baseline hydrogeological conditions. Previous regional- and intermediate-scale studies of the hydrogeological regime in the sedimentary succession in northeast Alberta are too coarse for the resolution needed for predictive modeling at the UTF site. The local-scale hydrostratigraphic delineation and hydrogeological and mineralogical characterization, which form the content of this study, will serve as a basis for numerical modeling of geochemical and hydrodynamic effects of deep injection of residual water at the UTF site.

In the local-scale study area there is sufficient information to refine the hydrostratigraphy and aquifer properties of Cretaceous strata only. Thus, information from the intermediate-scale study area has to be used for the hydrostratigraphy and hydrogeology of the Paleozoic strata. In the Cretaceous succession, the McMurray Formation is almost completely saturated with more than 3 mass-percent bitumen, thus behaving like an aquitard. The Wabiskaw Member of the Clearwater Formation is divided into a bitumen-saturated basal erosional channel, a lower shale wedge, upper sand and an upper regional marine shale. Only the Wabiskaw upper sand is an aquifer, possible target for injection. Above the remainder of the Clearwater Formation, which is a shaley aquitard, the Grand rapids Formation and Pleistocene strata form an unconfined aquifer. Mineralogical analyses show that dolomite is the dominant mineral in Winnipegosis Formation strata, calcite is the dominant mineral in the Calumet Member of the Beaverhill Lake Group, and quartz is the dominant mineral in the Wabiskaw Member sands. The Phanerozic aquifers at the UTF site are characterized in terms of petrophysical properties such as permeability, porosity and compressibility.