In the Pelican Lake area (T. 78-84, R. 17W4-2W5) oil reservoired in the Wabiskaw Formation is highly variable in terms of viscosity – a function of both primary and secondary processes. Primary processes affecting oil quality include source rock type and maturity. Secondary processes that can alter the initial oil quality include biodegradation, water washing, natural gas deasphalting, and oxidation in the presence of sulphate. Although most of the processes listed above affect oil density, oil viscosity may be additionally affected by sulphur and nitrogen content, gas-to-oil ratio, and possible CO₂ partial pressure. It is most likely that the dominant factor controlling oil density and viscosity variation is alteration. Since most of the alteration processes have an overall hydrogeologic control, analysis of the area’s hydrogeologic framework represents an important aspect of the required technical analysis.