Mesostructure Change in Land Facies Karamay Oil Sand Reservoirs Under Water Injection

Understanding the mesostructure of oil sand is significantly important in the exploration of Karamay oil sand since the effective permeability of water is largely dependent on pore structure. The objective of this study was to quantify and understand the meco-scale structure change on the Karamay oil sand samples subjected to shear dilation. Three popular laboratory methods in investigation of microstructure: mercury intrusion porosimetry (MIP), computer topography (CT) and scanning electron microscope (SEM), were conducted in order to disclose the change in pore structure of oil sand cores before and after mechanics experiments. The CT image shows the existing of oil sand shear bands. SEM reveals that a large number of micro-cracks are generated in the samples, and the smaller confining pressure during shear applied, the more obvious the shear band becomes. The result derived from MIP shows different pore size distribution after shear-- the proportion of micropores decreases, and total porosity increases. Meanwhile, acquisition method of several mesostructural parameters obtained by three techniques are put forward. Finally, based on the meso-scale structure change in oil sand specimen after triaxial shear test, the oil sand reservoirs performance under water injection is interpreted and evaluated.