Microscopic structure of athabasca oil sand

A refined structural model for in situ oil sands is proposed in terms of the mutual arrangement of sand grains, fines, water and bitumen. In the Athabasca deposit, the sand grains consist mainly of quartz and their packing is such that the porosity is about 35%. In rich oil sand, 10–15% of the pore space is occupied by connate water whereas the remainder is occupied by bitumen. For lower grade oil sands, a direct correlation exists between the water content and the amount of fines (particles smaller than 44 μm) and an inverse correlation exists between the bitumen content and the amount of fines. These relationships are successfully explained in terms of the irreducible water saturation in a porous medium and the double layer interaction between sand and bitumen surfaces.