In recent years, the exploration and development of shale oil and gas reservoirs has become a hot topic in various countries around the world. The mechanical properties of shale are an important basis for evaluating the mining effect. Previous studies have shown that shale swells with water, which greatly effects its mechanical properties. Based on the analysis of shale composition, a clay mineral swelling test and 3D compression test were carried out to analyze the influence of clay minerals on the mechanism of shale swelling and softening in water. The results show that hydration of clay minerals results in interlayer and intergranular swelling. Furthermore, an expansion force will be exerted on the rock skeleton. The clay minerals expansion will cause a decrease in the uniaxial compressive strength, decrease in the elastic modulus, and increase in the Poisson's ratio, both in normal and parallel directions to the shale plate bedding. The brittleness index calculated based on the elastic modulus and Poisson's ratio values also decreases. This work is significant for further engineering development of shale reservoirs.

中文翻译：

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页岩粘土矿物膨胀强度软化特性

近年来，页岩油气藏勘探开发已成为世界各国的热门话题。页岩的力学性质是评价开采效果的重要依据。先前的研究表明，页岩遇水膨胀，这极大地影响了其力学性能。在分析页岩成分的基础上，通过粘土矿物溶胀试验和三维压缩试验，分析了粘土矿物对页岩在水中溶胀软化机理的影响。结果表明，粘土矿物的水化作用导致层间和粒间膨胀。此外，膨胀力将施加在岩石骨架上。粘土矿物膨胀会引起单轴抗压强度降低，弹性模量降低，并且在与页岩板层理垂直和平行的方向上泊松比增加。基于弹性模量和泊松比值计算的脆性指数也降低。该工作对页岩储层的进一步工程开发具有重要意义。