Numerical simulations on compression behaviors of the laminated shale based on the digital image technology and the discrete element method

Abstract

Abstract As an unconventional reservoir sedimentary rock, the shale contains a series of layers and various microstructures that may lead to complex mechanical properties, such as the anisotropy of stiffness and strength. The present study is directed towards the anisotropy caused by the microstructures of the shale, where the 2D particle flow code (PFC2D) is adopted to explore the stiffness, strength, failure mode, and micro-crack evolution. More realistic microstructures and the calibration of microscopic parameters of the shale are reasonably considered through the computed tomography (CT) images and mineral analysis. The corresponding numerical simulation results are fully compared with the experimental results. In what follows, the sensitivity analysis is conducted on the key microscopic parameters and microstructure characteristics in numerical samples with laminated characteristics. The results show that the influence of microscopic parameters of the parallel bonding model on macroscopic parameters is related to the layering angle and the face type, and the microstructures and initial cracks of numerical samples can considerably affect the macroscopic mechanical behaviors of the laminated samples. Next, the effect of confining pressure on the mechanical properties of layered shale is discussed based on the numerical results. These findings highlight the potential of this approach for applications in micro-scaled models and calibration of microscopic parameters to probe mechanical behaviors of the laminated rock.