Mesoscopic Study on Seepage Characteristics with Shear Displacement in a Single Fracture

Abstract

To understand the change of fluid hydraulic behavior in the fracture under different shear displacements, fluid flow simulation at different flow velocity is carried out based on the Navier-Stokes equation. We characterize and make statistics on the change and distribution of fracture aperture under different shear displacements, especially the measurement of the contact area under shear displacement, which is helpful to accurately study the effect of shear displacement on fracture fluid flow. The research results show the shear displacement of the fracture can be regarded as the dislocation between the upper and lower fracture surfaces. The fluid flow velocity becomes larger near the contact sites, and the streamlines become denser. The resulting hydraulic aperture shows a negative correlation with the contact area. The relationship between volumetric flow rate and pressure gradient during flow field simulation can be well fitted by the Forchheimer equation, and the steepness of the curves is related to the contact area. The linear coefficient a and the nonlinear coefficient b in the Forchheimer equation are positively correlated with the contact area. From the measured flow velocity, the mechanical aperture is usually an order of magnitude larger than the hydraulic aperture. The linear relationship between mechanical aperture and hydraulic aperture is described. The positive correlation between permeability and mechanical aperture profiled during shear explains the hydraulic behavior in the flow field.