A numerical characterization workflow for assessing the strength and failure modes of heterogeneous oil sands

Understanding the strength and failure modes of overburdens and reservoirs is a critical component in safety assessments for oil sands surface mining and in situ thermal recovery operations. Currently, assumptions of homogeneity are often made for the geomechanical properties of oil sands in conventional slope stability analyses and reservoir simulation. The purpose of this work is to propose a numerical characterization workflow that helps predict the failure mode and shear strength of heterogeneous oil sands interbedded with shale beddings during thermal recovery. Heterogeneous models are generated through sequential indicator simulation with a calibrated constitutive model and geomechanical parameters for each lithology. Numerical simulations with boundary conditions reflecting in situ stress changes are conducted to study the impact of shale beddings on stress-strain response, failure modes, and shear strength of the sheared zone. The results show that shear failures of the weaker shale beddings play a significant role in the elastoplastic behavior and reduced shear strength of heterogeneous oil sands. The shear band and weak plane failures are found to be closely related to the volume fraction, variogram range ratio, and inclinations of shale beddings. The proposed numerical workflow allows for quantitative investigations of geomechanical response for rock mass with complex lithological heterogeneities.

Automated summary

This study proposes a numerical characterization workflow to predict the failure mode and shear strength of heterogeneous oil sands interbedded with shale during thermal recovery. The results show that shear failures of weaker shale play a significant role in the elastoplastic behavior and reduced shear strength of heterogeneous oil sands. The proposed numerical workflow allows for quantitative investigations of geomechanical response for rock mass with complex lithological heterogeneities.