||The heavy oil accumulation at Cold Lake is part of the Lower Cretaceous heavy oil deposits that occur in a discontinuous trend in the eastern half of the western Canadian basin (Figure 30-1). This trend extends from the Peace River deposit in northwestern Alberta through Wabasca, Athabasca and southwards to Cold Lake and Lloydminster. The Cold Lake deposit is located 300 km northeast of Edmonton, covers over 6,500 km2, is the second largest oil sands deposit in Canada, and contains more than 20 X 109 m3 (125 billion barrels) of heavy oil in place. This oil, or bitumen, is a low gravity, high viscosity fluid which, under reservoir conditions, is immobile. The minimum depth to the first oil sand at Cold Lake is 300 m and this dictates that production must be by some in situ process. These are very costly and, as such, must be well planned and designed. Reservoir description plays a key role in the selection of the location for a scheme, in the planning of a specific recovery process, and in the analysis and prediction of production performance.