Hydrogeological and geothermal regimes in the Phanerozoic succession, Cold Lake area, Alberta and Saskatchewan

The natural, steady-state fluid flow and geothermal regimes were determined for a region defined as Tp 50-70, R 15 W3M to R 17 W4M (60 000 km2), including the Cold Lake Oil Sand Deposit and adjacent heavy oil areas to the south. The study was based on information from 14 800 wells, 1858 analyses of formation waters, 2155 drillstem tests, 46 700 core analyses, and 19 218 bottomhole temperature measurements. Data processing was carried out using specially designed software developed by the Basin Analysis Group.

Regional geology was synthesized in terms of definable stratigraphic successions, and individual, lithologically distinct stratigraphic units were characterized by structure contour and isopach maps. The fluid flow and geothermal regimes for individual aquifers, aquitards, and aquicludes were described using isopach, salinity distribution, potentiometric surface and temperature distribution maps, together with pressure-head as depth plots and hydraulic head cross sections. Based on this information the hydrostratigraphic units can be grouped into ten aquifers and aquifer systems (Lower Paleozoic, Winnipegosis, Beaverhill Lake, Camrose Tongue, Grosmont, Winterburn, McMurray, Clearwater, Mannville, and Viking), four aquitards and aquitard systems (Ireton, Clearwater, Joli Fou, and Colorado) and three aquicludes and aquiclude systems (Precambrian, Lower Devonian, and Prairie). Oil sand layers act as intermediate to weak aquitards, and lateral flow probably bypasses them.

Lateral flow is dominantly regional to the northeast in aquifers in the Lower Paleozoic and Middle Devonian. In the McMurray and Clearwater aquifers lateral flow is of the intermediate type to the west and northwest under the influence of a drain effect by the underlying Grosmont aquifer system. Lateral flow in the Mannville aquifer is indeterminate, being intermediate to local, while lateral flow in the Viking aquifer (within the Colorado aquitard system) is also intermediate to local, and topographically controlled.

Heat flow is mainly conductive, the convective component being negligible due to the low permeability of the rocks. The integral geothermal gradient is strongly dependent on the average thermal conductivity of the sedimentary column, which in turn depends on the Ethology of the strata. As a result, the integral geothermal gradient is highest in the areas with a thick section of Ireton shale and lowest in regions where halite is present without overlying Ireton shale.

The synthesis of this vast amount of information on the natural fluid flow and geothermal regimes in the study area was carried out under a jointly funded contract between the Alberta Research Council and Alberta Environment in preparation for the evaluation of deep waste injection in the Cold Lake area.