5 / 2025-03-11 10:10:22

An investigation of permeability characteristics of a roughness fracture with internal contacts based on the Lattice Boltzmann Method

Lattice Boltzmann Method,Fracture permeability,Multi-scale roughness,Contact ratio

The geometric morphology of natural fractures usually exhibits surface roughness and internal contacts with the influence of crustal stress and engineering disturbance. This study investigates the influence of fracture geometry, including roughness and internal contacts, on flow characteristics employing the Lattice Boltzmann Method (LBM) with low Reynolds numbers. Wavelet transform technique is applied to investigate the effects of multi-scale roughness on fracture permeability by integrating the advantages of the LBM in handling complex boundary conditions. Numerical results indicate the generation of vortices and backflows around small-scale roughness and internal contact areas within fractures is the primary reason for the weakening of inertial effects of fracture flow. The large-scale roughness of fractures determines the pattern of the flow lines. A quantitative relationship is established between the large and small-scale roughness of fractures, the internal contact ratio, and the permeability of fractures. The permeability of fractures decreases with the increase in roughness and contact ratio. At lower internal contact ratio within fractures, augmentations in both macro- and micro-scale roughness markedly contribute to the diminution of fracture permeability. In contrast, at elevated contact ratio, the influence of increased roughness on the permeability of fractures becomes considerably attenuated. This work provides a method for predicting permeability through the complex geometric characteristics of fractures, which helps the quantitative evaluation of the seepage regularity in a fracture.