ABSTRACT: Oil sand, a kind of porous media, contain a naturally occurring mixture of sand, clay, water, and viscous bitumen. The shear behavior of oil sands is quite different from hard rock due to the special microstructure. As the unconsolidated structure of oil sands, it is particularly difficult to characterize the shear-induced microcrack of it. The oil sands specimens from Karamay, treated as 25×50 mm standard core pillar, were scanned before and after the triaxial compression test and a total number of 3400 grayscale images were obtained respectively. The grayscale images are segmented into 3 discrete phases (sand grain, bitumen, and pore) and used for digital core construction, then the microstructural deformation is analyzed. At the same time, the variation of porosity, pore radius, and throat radius were quantitatively analyzed by the pore network model. The results show that there is a shear band with discontinuous microcracks inside rather than a macro crack in the oil sands cylinder after shearing. The shear dilation is caused by different types of microcracks (microcrack in bitumen, microcrack between sand grains, and microcrack between bitumen and sand grain) in the shear band. Outside the shear band, several dense zones were observed with less void space.

Keywords:
oil sand, shear band, particle, sand grain, complex reservoir, pore, characteristic, upstream oil & gas, core technology, compression test
Subjects:
Unconventional and Complex Reservoirs, Oil sand, oil shale, bitumen
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