Characterization and Numerical Simulation of the Microstructural and Micromechanical Viscoelastic Behavior of Oil Sands Using the Discrete Element Method

摘要

Oil sands are naturally geologic formations of predominantly quartz sand grains whose void spaces are filled with bitumen, water, and dissolved gases. The electric rope shovel is the primary equipment used for excavating the Athabasca oil sand formations. The equipment's static and dynamic loads are transferred to the formation during excavation and propel. These loads may reduce the oil sand shear strength and cause instability leading to sinkage or rutting, crawler wear, and fracture failures. These problems result in unplanned downtimes, production losses, and high maintenance costs. In order to address these problems, there is a need to develop valid models that capture the behavior and performance of oil sands under these loads. Particle-based physics methods, such as the discrete element method (DEM) can provide useful insight into the micromechanical and microstructural behavior of oil sands. This research is a pioneering effort towards contributing to the existing body of knowledge in oil sands formation characterization and numerical simulation using the DEM. These areas include oil sands as a four-phase material, shovel-formation interactions, and coupled deformation-stress under dynamic loading. A 2-D DEM model of the oil sands is built and simulated in PFC2D. The simulation results show that the generalized Burgers model with five Kelvin---Voigt elements fully characterized the microscopic viscoelastic response of the material. The micromechanical and microstructural viscoelastic model developed in this study can predict the dynamic modulus and phase angle of the material with a maximum error of 13.6%. This research initiative is a pioneering effort toward understanding shovel-oil sands formation interactions using a micromechanical and microstructural particle-based mechanics approach.