REGIONAL GROUNDWATER MANAGEMENT FOR OIL SANDS DEVELOPMENT, ALBERTA, CANADA

The supergiant Athabasca and Cold Lake Oil Sands deposits of northeast Alberta, Canada, are undergoing massive commercial development. Where overburden is too thick for surface mining, in-situ thermal techniques are used to deliver steam into reservoirs and extract bitumen-water mixtures for surface processing. Groundwater management is key to profitable and environmentally sustainable recovery of oil-sands bitumen.

In the area of in-situ development, groundwater is the predominant source of water for steam. The groundwater may be fresh or brackish, depending on location. The major source of fresh groundwater is a regional system of buried pre-glacial and glacial channel aquifers. These aquifers are hydraulically connected to lakes and rivers so their development will require co-management with surface water resources. Model-based techniques like transition-curve analysis have been found to be helpful in framing water-resource planning policy. However, the sheer size and remoteness of the area under development has meant that only first-order estimations of regional-scale groundwater-surface water interactions have been made despite over three decades of hydrogeological attention.

Development of brackish groundwater resources creates saline waste-water requiring disposal. The favored method of disposal is underground injection. Natural capacity for underground injection varies from very good to very poor, again depending on the area. Injectivity and storage capacity is often limited by bitumen saturation. Away from the bitumen, the degree of hydraulic connectivity to downcut and often buried glacial scours and modern river courses must be considered before underground injection sites are approved.

Some oilfield solid-waste like lime-sludge from water-softeners must be surface disposed. The complex glacial and post-glacial history of the area has created a composite land-surface consisting of widespread glaciolacustrine and modern organic deposits sitting atop thick clay tills and sandy tills vertically punctuated by downcutting glacial and post-glacial meltwater channels and modern stream courses. Characterization of the surficial geology is needed to inform best-practices in oilfield waste management and protect shallow groundwater quality.