基于CT扫描的岩心压敏效应实验研究

为揭示岩石应力敏感的微观力学机理,加深对应力敏感性的理解,基于可以真实描述岩石内部结构特征的CT扫描技术,结合数字岩心和孔隙网络模型理论进行了几何拓扑结构分析,获得了有效应力与孔隙结构的关系及有效应力与渗透率的关系,对比了有效应力升高、降低2个过程中的孔隙结构参数和渗流能力。结果表明:随着有效应力升高,孔隙半径分布曲线向左偏移,形状因子概率曲线向右偏移,孔喉连通性变差,渗透率降低;随着有效应力降低,孔隙半径分布曲线、形状因子概率曲线、孔喉连通性和渗透率的变化规律均与有效应力升高时相反。孔隙结构变形存在应力敏感滞后性,且有效应力降低后渗透率不能恢复。这说明应力敏感对于岩石孔隙的变形以及流体在其中流动的影响不能忽略。 

Experimental Study on the Pressure Sensitive Effects of Cores Based on CT Scanning

In order to reveal the microscopic mechanical mechanisms of rock stress sensitivity and to further understand stress sensitivity, a geometry and topology structure analysis was carried out using CT scanning technology which could show the actual internal structure characteristics of rocks, and can be combined with digital cores and a pore network model. Following this procedure, the relationships between effective stress,pore structure and permeability were obtained, and pore structure parameters and percolation capacities were compared during the increase and decrease of effective stress. It is shown that with the increasing of effective stress, the pore radius distribution curve shifted to the left, the shape factor probability curve shifted to the right, the pore throat connectivity became worse resulting in a decrease in permeability, and vice versa. The pore structure deformation was characterized by stress sensitivity hysteresis. After the effective stress dropped, permeability could not fully recover. In summary, it is necessary to pay attention to the effect of stress sensitivity and fluid flow on the deformation of rock pores.