【摘要】 为了研究二氧化碳压裂液对煤体力学特性的影响规律,以陕北典型侏罗纪煤层为研究对象,利用自主研发的煤岩体多场多相耦合压裂试验系统,开展不同二氧化碳压裂液、不同条件(时间、温度和浸泡压力)下的煤体浸泡试验,通过单轴压缩与巴西劈裂力学测试,分析二氧化碳压裂液对煤体力学特性的影响规律,同时结合X射线衍射(X-ray diffraction,XRD)、扫描电子显微镜(scanning electron microscope,SEM)对煤体的微观测试,分析二氧化碳压裂液与煤体的相互作用机制。结果表明:二氧化碳压裂液浸泡后煤体的峰值强度、弹性模量、抗拉强度与软化系数均出现不同程度的下降;二氧化碳压裂液作用煤体过程中,煤体的峰值强度、弹性模量与软化系数受温度、浸泡压力影响较大,且对煤体强度弱化幅度超过30%;在二氧化碳压裂液作用下,一方面改变煤体颗粒骨架与孔隙结构,另一方面改变煤体中的矿物组分,降低矿物颗粒间的联结力,从而弱化煤体的力学特性。研究成果为低渗硬厚煤层二氧化碳耦合压裂参数设计优化提供参考。更多还原

【Abstract】 In order to study the influence of CO₂fracturing fluid on the mechanical properties of coal body, taking the typical Jurassic coal seam in northern Shaanxi as the research object, using the self-developed coal rock mass multi-field multi-phase coupling fracturing test device, coal immersion tests under different CO₂fracturing fluid and different conditions（time, temperature and immersion pressure） was carried out, and the influence of CO₂fracturing fluid on the mechanical properties of coal body was analyzed through uniaxial compression and Brazilian splitting mechanical test, and the microscopic test of coal body combined with X-ray diffraction（XRD）and scanning electron microscope（SEM） was carried out. The interaction mechanism between CO₂fracturing fluid and coal was analyzed. The results show that the peak strength, elastic modulus, tensile strength and softening coefficient of coal after immersion of CO₂fracturing fluid decreases to varying degrees. During the application of CO₂fracturing fluid to the coal body, the peak strength, elastic modulus and softening coefficient of the coal body are greatly affected by temperature and immersion pressure, and the weakening range of the coal strength exceeds 30%. Under the action of CO₂fracturing fluid, on the one hand, the skeleton and pore structure of coal particles are changed, and on the other hand, the mineral components in the coal body are changed, and the bonding force between mineral particles is reduced, thereby weakening the mechanical characteristics of the coal body. The research results can provide a reference for the design and optimization of construction parameters of carbon dioxide coupled fracturing in low-permeability hard and thick coal seams.更多还原