三维颗粒流数值模型的胶结砂岩力学特性

为了更好地反映砂岩胶结性状对力学特性的影响,以油藏储层砂岩为研究对象,建立基于平行粘结接触的三维颗粒流数值模型(PFC3D)用以模拟剪切试验中砂岩结构的破坏机理.进行PFC3D的二次开发描述平行粘结分布和力学性质,分析剪切过程中砂岩体应力比、体应变、配位数和粘结破坏与应变之间的关系,通过接触网络的演化说明力链的重要作用,验证了数值模型的可行性.对比研究了不同胶结半径比、平行粘结刚度和胶结量变化对胶结砂岩力学特性的影响,阐明了胶结性状对砂岩结构受力的控制作用,为建立特定条件的胶结砂岩破坏机理提供了科学依据.

Research on Mechanical Characteristics of the Cemented Sandstone Based on 3Dimensional PFC Numerical Model

Sandstone is sediment rock composed of many cemented sand particles, and corresponding particle constraint and force bearing capacity are greatly controlled by the cemented property. In order to better reflect the cemented property influencing on the mechanical characteristics of the sandstone, take the oil sandstone reservoir for instance, a numerical model based on 3Dimensional Particle Flow Code (PFC3D) considering the parallel bond model was brought forward to simulate the failure mechanism during shearing process. The sandstone cemented property is modeled based on random mathematics and advanced development of Particle Flow Code (PFC), and the relation of the stress ratio, volume strain, coordination number and bond-broken number and the axial strain is analyzed in detail, especially the contact network evolution indicated the force chain is important to transfer the external force, which verifies the feasibility of the numerical model. Based on the above PFC3D model, a series of researches on changing the cemented radius ratio, parallel bond stiffness and cemented volume of the particles have been done to clearly illuminate the importance of cemented property for the bearing capacity of the sandstone structure, which provides a scientific base for research on the failure mechanism of the sandstone under special conditions. Therefore, the above numerical method is more efficient and applicable for comparatively large scale and complex experiments, and the obtained research results can bring a new thought for the real cemented sandstone to research on its macro-micromechanical response and the structure failure mechanism, and also is significant for the sand production mechanism, sand volume prediction and sand control measures for the sandstone reservoir.