The evolution of geometry and flow characteristics of fracture inside tight sandstone under stress

The evolution of geometry and flow characteristics under stress is of great significance for many natural and technological processes. In this paper, a three-dimensional rough single fracture model is reconstructed based on three-dimensional morphology scanning technology. The geometric deformation and flow characteristics of natural fracture inside tight sandstone under varied shear displacements and loads are simulated using the finite element method. The results show that the primary factors causing variations in flow characteristics are geometrical deformations under stress such as reduced apertures, expanded contact areas, and degradation of roughness. With the increasing stress, the aperture and contact area of the fracture would experience an evident decrease and increase, respectively, leading to an increase in the flow resistance. Simultaneously, the degradation of roughness would exacerbate these changes in the aperture and contact area. For the rougher fracture, the permeability and flow area can be maintained higher value due to its smaller geometric deformation and a more uniform stress distribution. Furthermore, shear displacement modifies the mismatch between the top and lower fracture surfaces, resulting in a decrease in flow rate and permeability.