Abstract
To design and optimize hydraulic fracturing technology for shale gas production, it is crucial to understand the impact of mineral composition on shale mechanical properties. In this study, based on the Brazilian splitting experiment results of Weiyuan shale, a heterogeneous mechanical numerical simulation model of shale is established, and Brazilian splitting tests are conducted . Then, the influence of mineral size, mineral spatial distribution, critical failure displacement, and the stiffness of interface elements on fracture propagation is analyzed. The results indicate that with the increase of the mineral size, the tensile failure ratio decreases from 0.5 to 0.4, and a more complex fracture path is formed. Meanwhile, the changes in the spatial distribution of minerals also lead to certain differences in the simulation results. This phenomenon may be caused by the nonuniform distribution of mineral components in heterogeneous shale, which leads to a significant difference in the stress path and stress concentration location. Therefore, the crack initiation and propagation trajectories show certain differences. With the increase in critical failure displacement of the interface element, the failure stress of the Brazilian split specimens gradually increased from 6.2 kN to 7.92 kN, and the tensile strength increased. When the stiffness of the interface element is high, local shear failure dominates, and the failure mode is manifested as single brittle failure. This result indicates that the mechanical properties of the fracture interface inside and outside the mineral have a significant impact on the Brazilian splitting process of shale. Therefore, further consideration of the influence of the interface on the propagation law of Brazilian splitting fractures in shale is an important way to clarify the propagation law of Brazilian splitting fractures in shale. This study can provide important reference for understanding the deformation and fracture characteristics of shale under the influence of minerals.