页岩微观结构及力学特征变化规律研究

A Study on the Law of Microstructure Changing and Mechanical Properties of Shale

目前,对二氧化碳作用下页岩微观结构及岩石力学变化特征认识较少,为更清晰地认识二氧化碳对页岩微观结构及力学特性的影响,设计并开展了二氧化碳浸泡前后页岩岩石力学参数测试实验、矿物组分分析及微观结构分析。研究表明,滑溜水、超临界二氧化碳及液态二氧化碳浸泡基本不会改变页岩的矿物组成,二氧化碳浸泡会增大页岩矿物间孔隙;单轴实验条件下,随浸泡时间的增加,泊松比增大,弹性模量减小,整体上页岩表现出塑性增强特征;三轴实验条件下,随浸泡时间的增加,泊松比减小,弹性模量基本不变,整体上页岩表现出脆性增强特征,其中,二氧化碳浸泡的影响更为显著;滑溜水、超临界二氧化碳及液态二氧化碳浸泡均会降低页岩抗拉强度,滑溜水对抗拉强度的弱化程度最大,3种介质对抗压强度影响较小。

Currently,there is less knowledge about the effect of carbon dioxide on the microstructure and mechanical properties of shale;this study aims to obtain some parameters through designing the special experiments for researching the effect of carbon dioxide on shale.Results show that mineral composition cannot be changed after shale soaked by slick water,supercritical carbon dioxide and liquid carbon dioxide,but porosity of shale could be scaled up;as bathing time goes up,Poisson′s ratio increases and elastic modulus decreases under uniaxial compression condition,which expresses plasticity characteristics of shale is more obvious;under triaxial compression test,Poisson′s ratio goes down and elastic modulus is affected scarcely by those working fluid,which tells brittleness of shale is stronger than before,and carbon dioxide has best performance;tensile strength declines with soaking time goes away,and slick water performs better than carbon dioxide;compressive strength hardly weakened by three types of liquids.