Surface mining of oil sands is generally limited to areas where the overburden thickness is less than ~75 m. Oil sands consist of a mixture of coarse sands, fine mineral solids, clays, formation water, and bitumen. Usually the orebody varies from 20 to 90 m in thickness, and the oil sand formation deposit is not homogeneous as it is intermingled with clays lenses (interburden). Bitumen content has been traditionally used as an indicator of ore processability. In fact, ores with a bitumen content of below 7% are considered uneconomical for processing. In this study, four types of ores were selected to evaluate the effect of adding two types of interburden with high clay contents on their ore processability. Ore processability was tested using the batch extraction unit. It was found that the interburden dilution does not always detrimentally affect the recovery. Depending on the ore grade, interburden dilution may boost the recovery for coarse grained ores, and depress the recovery for average and low grade ores. Current operational use of a maximum allowable fraction of interburden blended into oil sand feed may be overly simplistic. The results suggest that dilution to a maximum fines content of the blend is required rather than to a maximum fraction of interburden. Interburden effect on tailings settling behavior was also studied.

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