微观渗流模型均质程度和宏观特性的界定

Determination of homogeneity and macroscopic features of microscopic seepage models

针对传统微观渗流研究方法中存在的不足,提出自相关函数的概念及其性质,并结合二维图像实例,确定出图像的自相关长度,以此来表征多孔介质的均质性.进一步研究了不同区域内图像的孔隙度变化,指出图像在某方向上具备宏观意义的前提条件是该图像的尺寸必须满足大于10倍自相关长度.在二维图像的基础上,结合三维空间特点,分别研究了不同方向上自相关函数特点,结果表明,只有当三维空间中不同方向上自相关函数达到一致且满足大于10倍自相关长度的时候,微观模型才具有宏观均质性,并且具有宏观意义,此时的微观模型才能代表储层宏观特性.

Aiming at the shortcomings of traditional seepage research methods,the concept of autocorrelation function and its property are proposed. The autocorrelation length of 2D images of actual porous media is determined,by which the homogeneity of porous media can be characterized. The variety of the porosity of the different areas in the same image is studied,and the result indicates that the condition for an image having the macroscopic features in some direction is that the size of the image should be larger than 10 times of the autocorrelation length. On the basis of 2D images,the features of autocorrelation functions of a 3D image in different directions are studied,the result shows that only when the autocorrelation functions in different directions achieve to the consistence and the size of the image must be larger than 10 times of the autocorrelation length,the microscopic seepage model will be of homogeneity and macroscopic features. Only in this case can the microscopic seepage model represent the macroscopic features of porous media.