It is of great significance to understand the flow behavior in rough fractures for unconventional resource develop-ment,such as shale gas and oil. In this study,a Gaussian function was introduced to describe the fracture surface property based on the fracture surface height distribution in shale rocks. A 3D rough fracture model was built in the consideration of different parameters,including roughness,fractal dimension,mismatch length and anisotropy. A Lattice Boltzmann method combined with the orthogonal experimental results and grey correlation analysis was adopted to study the flow behavior in 3D mismatch rough fractures. The results show that the permeability in rough fractures is approximately 20%-50% of that in parallel plate fractures,and the permeability in mismatched fractures is slightly lower than that in matched fractures and a backflow may occur in the mismatched area. In order to ensure the fracture aperture,it should avoid to engender a mismatch in fractures,and decrease the fracture surface roughness and fractal dimension. The aperture and roughness of fracture are the two most important influencing factors to the fracture permeability, and the fractal dimension, anisotropy and mismatch length are also important factors. The roughness distribution along the fracture surface also has a great influence on the frac-ture permeability. In the case study of shale rocks,with the anisotropic coefficient increases,the fracture permeability firstly increases and then decreases,with a maximum value appears when the anisotropic coefficient is 0.7.%掌握裂缝结构中的渗流规律对合理开发非常规资源具有重要意义.基于页岩裂缝面高度分布特点,引入Gaussion分布函数并综合考虑粗糙度、分形维数、非匹配性和各向异性等构建三维裂缝的数学模型;采用Lattice Bolt-zmann方法结合正交试验和灰色关联分析系统研究三维非匹配性裂缝中流体的渗流规律.结果表明:研究中裂缝渗透率约为平板模型的20% ~50%;非匹配区域结构的突然变化极易产生回流区,导致裂缝渗透率减小;在保证开度情况下,尽量避免产生裂缝的非匹配性,降低其粗糙度和分形维数;裂缝开度和粗糙度是影响裂缝渗透率的最主要因素,其他依次为分形维数、各向异性系数和非匹配长度;实例中裂缝渗透率随各向异性系数增加先增加后降低,并在各向异性系数为0.7时达最大值.
展开▼
