Time-dependent damage characteristics of shale induced by fluid–shale interaction: a lab-scale investigation

The shale’s multi-scale mechanical behaviors were investigated to understand the time-dependent damage characteristics induced by shale–fluid interaction. The test results indicate that, as fluid–shale interaction proceeds, the mechanical strength of shale has undergone a weakened to an enhanced process as interaction proceeds, and the size distribution of fragments tends to be more uniform, leading to a positive correlation between the mechanical strength and fractal dimension. Within 2 weeks of fluid–shale interaction show a decreasing trend for the fractal dimension of fragments in post-failure and cause less than 2 mm for the dominant size of fragments. The dominant size increases to greater than 30 mm when the fluid–shale interaction is over 2 weeks. Finally, the correlation dimension associated with ring counts of acoustic emission (AE) at each loading stage is determined in terms of the G-P algorithm to predict the damage degree of shale.