Nanoindentation Study on Microscopic Mineral Mechanics and Bedding Characteristics of Continental Shales

The brittle minerals and shale bedding seriously affect the fracture performance of shale, and macroscopic mechanical experimental methods cannot separate these key factors for analysis. In this study, nanoindentation tests were conducted on clay and carbonate shales, and the effects of felsic minerals on the micromechanical characteristics of shale were evaluated.Based on the extended cavity model, the analytical formulas for energy density and total energy function during the indentation process of layered shale were discussed. The results showed that with the increase of felsic mineral content, clay shale exhibited brittle mineral depression in the indentation test, while carbonate shale exhibited obvious crack propagation and brittle fracture. The dimensionless brittleness index of carbonate shale is greater than that of clay shale, and an increase in the content of felsic minerals will further increase this index. The influence of bedding morphology on shale indentation energy is relatively small, while the mechanical properties of minerals determine the mechanical performance of shale. The research results of this article can serve as an important supplement to macroscopic rock mechanics experiments and contribute to a more in-depth study of the mechanical properties of heterogeneous layered shale reservoirs.