Primary recovery of bitumen from the Athabasca oil sand is variable throughout the deposit. The common empirical equation for estimation of primary recovery (based on weight percent fines and oil saturation) does work well in the marine zone. Fourier grain shape analysis and accompanying scanning electron microscopy were used to see whether the sand fraction characteristics varied within the Syncrude Canada Ltd. minesite and whether these might be associated with low primary recovery in sands otherwise expected to yield high primary recovery. Sand grains varied in surface roughness from very smooth to extremely irregular.

Primary recovery of bitumen, via the Clarke Hot Water Extraction process, is reduced when oil remains in the primary tailings. Using a batch extraction unit simulator of the hot water extraction process and Fourier grain shape analysis we found that the primary recovery of bitumen is reduced in marine zone when there is a high percentage of irregular (high surface area) grains in the oil sand. These irregular grains appear to be diagenetically altered quartz and rock fragments. The relationship exists that when there is a high proportion of irregular grains in the oil sand, oil is held by the rough surfaces of the sand grains in the primary tailings. Apparently the irregular sand is at least partially oil wet and so oil accumulates with such grains in the primary tails. Thus when the proportion of irregular sand is greater than 40%, oil stays in the tailings reducing the primary recovery.

Analysis of these sands in thin section and by scanning electron microscopy shows an abundance of irregular grains which are mostly lithic fragments (volcanic and sedimentary rock fragments). We postulate that these lithic fragments have different wettabilities than say smooth quartz grains of the channel sands. This may explain why low fines oil sands in the marine zone process so poorly.