ABSTRACT: Environmental Constraints on Deep Disposal of Liquid Wastes in the Athabasca Oil Sands Area

BACHU, STEFAN, and JAMES R. UNDERSCHULTZ, Alberta Geological Survey, Alberta Research Council, Edmonton, Alberta, Canada

The Athabasca Oil Sands deposits are situated in the shallow northeastern part of the Western Canada sedimentary basin in Alberta, Canada. Open pit mining is used for bitumen extraction in areas where the deposits are close to the surface, while steam-based enhanced oil recovery methods are used for extraction from deeper strata. Large amounts of residual water are produced in both cases. Currently, the residual waters at the mining operations are disposed of in tailings ponds. Because these ponds are close to full capacity, consideration is being given to injecting the liquid waste in deep formations. Deep injection is also envisaged for the disposal of residual water at underground extraction sites such as the Underground Test Facility of the Alberta Oil Sands Technology and Researc Authority (AOSTRA), near Fort McMurray.

Generally, three types of constraints need to be considered in the hydrogeological evaluation of sites for deep injection of liquid wastes, broadly relating to: (1) the natural hydrogeological regime; (2) the integrity of the injection aquifer and adjacent hydrostratigraphic units; and (3) protection from contamination of existing and potential economic, mineral, and water resources. In the Athabasca Oil Sands area, particular conditions impose more restrictions on the ability to dispose of liquid wastes by injection. These are the result of basin shallowness, of the internal hydrostratigraphic structure of the sedimentary rocks, and of the erosion and outcropping of Cretaceous and Devonian strata both along the Athabasca River drainage system and toward the basin edge. The hydrogeolo ical characteristics of the Phanerozoic strata and the specific environmental constraints to deep injection of liquid wastes in the Athabasca Oil Sands area will be presented.

AAPG Search and Discovery Article #91012©1992 AAPG Annual Meeting, Calgary, Alberta, Canada, June 22-25, 1992 (2009)