ABSTRACT:

The fracture energy of the shale possesses a significant anisotropy due to the shale bedding and has great effects on the fracturing path. To investigate these effects, three types of the shale specimens are applied in fracturing test with three-point bending. The Digital Imaging Correlation (DIC) and Acoustic Emission (AE) methods are also integrated to analyze the damage processes. According to the AE energy, the damage process of the shale can be divided into three parts using the proportion between the loading value and the peak value of the specimen. In Part I, the sample does not damage. In Part II, the damage begins to appear in the sample, and the work of the external forces is mainly contributed to create the new cracks in the rock layers and to promote the opening and dislocation of the layer interfaces. In Part III, the cracks develop because the damages in the shale are accumulated to an extreme value. Fracture energy anisotropy extent of the shale has been obtained from these partitions, which can be further applied to optimization of the perforation and hydraulic fracturing direction.

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