Comparative Study of the Mechanical and Fracturing Behaviors of Shale from Different Gas Blocks in the Longmaxi Formation.

Abstract

With the development of shale gas exploration and exploitation, the mechanical and failure characteristics of shale have become one of the focuses. However, few studies have considered the differences in the mechanical properties of shales in different shale gas blocks. In this study, the effects of bedding orientation on the stress-strain curves, elastic modulus, Poisson's ratio, and fracture morphology of shale samples from the Zhaotong block are analyzed by laboratory experiments, first. Then, a standard deviation method is used to characterize the anisotropy degree of the mechanical and fracturing characteristics of shale. The anisotropy ratio of shale samples between the Zhaotong and Chongqing areas has been comparatively studied. Comparison results show that the shale anisotropy induced by the bedding orientations demonstrates apparent regional characteristics. There are significant differences in the mechanical properties of shale obtained from different shale gas blocks. It indicates that the optimization of engineering practices such as the design of hydraulic fracturing should consider the influences of the bedding orientations and shale gas blocks on the shale anisotropy.