Drilling and multi-stage hydraulic fracturing bring a large amount of water into clay-bearing shale reservoirs, which may lead to attenuation of fracturing effects and wellbore instability. However, a thorough understanding of changes in shale micromechanics and corresponding mechanisms when exposed to water remains unclear. In this work, samples were selected based on clay enrichment. Subsequently, the contact resonance (CR) technique based on atomic force microscopy (AFM) was performed to characterize the micromechanics of shales after exposure to water. Visual phenomena provided by environmental scanning electron microscopy (ESEM) assisted to explain the underlying mechanisms. It was found that the hydration effect lowered both the storage modulus and stiffness of samples, but with different contributions from brittle minerals and clay, as well as variations depending on bedding plane orientation. Due to the difference in composition, the investigated terrestrial shale material exhibited stronger water sensitivity and anisotropy, with a general decrease of 15%–25% in storage modulus, compared with variations of -5%–15% in modulus of marine shale samples. Moreover, microscopic observation experiments revealed that the reduction of capillary force and the interlaminar swelling of clay particles might have been active after water adsorption, which led to the decreases of modulus and stiffness values. However, the swelling-caused confining effect or void space closure during the water imbibition process might have offset this weakening effect and even increased storage modulus. At mesoscale, excessive shrinkage caused the growth of micro-cracks, which in turn significantly attenuated overall mechanical properties.

钻井和多级水力压裂将大量水带入含粘土页岩储层，可能导致压裂效果衰减和井筒失稳。然而，对暴露于水时页岩微观力学和相应机制的变化的透彻了解仍不清楚。在这项工作中，样品的选择基于粘土富集。随后，基于原子力显微镜的接触共振（CR）技术(AFM) 用于表征暴露于水后页岩的微观力学。环境扫描电子显微镜 (ESEM) 提供的视觉现象有助于解释潜在的机制。发现水化效应降低了样品的储能模量和刚度，但脆性矿物和粘土的贡献不同，并且随着层理平面方向的变化而变化。由于成分的差异，所研究的陆相页岩材料表现出更强的水敏感性和各向异性，与海相页岩样品的模量变化-5%-15%相比，储能模量普遍下降15%-25%。此外，显微观察实验表明，毛细管力的降低吸水后粘土颗粒的层间膨胀可能活跃，导致模量和刚度值降低。然而，吸水过程中膨胀引起的限制效应或空隙空间封闭可能抵消了这种削弱效应，甚至增加了储能模量。在中尺度上，过度收缩会导致微裂纹的生长，进而显着降低整体力学性能。