Experimental Study on Hydration Characteristics of Organic-Rich Shale

In order to reveal the hydration damage mechanism of organic-rich shale, the hydration characteristics of Longmaxi shale in Changning area were studied by means of XRD diffraction, spontaneous imbibition, immersion, hydration stress, hydration strain and other physical experiments. The results show that the organic-rich shale is mainly composed of clay minerals and quartz, and the main composition of clay minerals is illite and illite smectite mixed layer, without montmorillonite. Hydration occurs during the process of self-water absorption of organic-rich shale, and the higher the content of clay minerals, the greater the spontaneous imbibition, the more likely hydration reaction occurs. The hydration of organic-rich shale is more intense in the early stage of the reaction and gradually tends to be stable in the later stage. The initiation, expansion and confluence of cracks in the hydration process could be observed and they gradually evolved into macro-penetrating fractures. The linear hydration stress of illite is slightly less than that of montmorillonite, but the hydration strain is much less than that of montmorillonite. The non-uniform hydration of different clay minerals and the mixed layers leads to the hydration damage phenomenon of organic-rich shale.