Identification of Shale Bedding Layers from Micromechanical Evaluation

Abstract Bedding layers are well-developed in shale and recognized to enhance the complexity of the hydraulic fracture network. A micromechanical evaluation approach of shale bedding layers based on indentation testing techniques was proposed. Rock thin section identification and scanning electron microscope were utilized to describe the shale laminations. To capture high-resolution image with large area and ensure abundant morphology and mineral information, Atlas 5 system, which could create large mosaic images, was applied. Combined with FIB, a method for positioning the laminations in SEM and accurately navigate to it in the micromechanics experiment was established. Fractures were emphasized to be initiated and extend in the clay mineral layers. It can be explained that the flaky structure of clay mineral is beneficial for the extension of fracture. It will become more potential to connect with the fluid-driven fractures. Nanoindentation was conducted to obtain micromechanical properties in different lamination layers. Results verify the feasibility of this scheme and demonstrate fine-grained, transition and coarse-grained layers. Indentation results show variation in micromechanical properties of coarse-grained layer, the transition layer and the fine-grained layers. The present work is helpful to identify shale bedding layers from micromechanical evalutions.