弥散系数在非均质多相岩层中的尺度效应

根据渗透系数在多相岩层中的协方差函数,文中首先推导了用以描述溶质在三维模型中运移特征的宏观弥散系数方程,然后导出了纵向弥散系数用来表达该参数的尺度效应。利用一个例子,讨论了宏观弥散随时间的变化趋势,以及同一岩相内转移项和越相转移项对弥散的相对贡献。灵敏度分析指出纵向弥散系数是与岩相平均长度正相关,也与不同岩相的渗透系数的差值正相关,其取值随渗透系数的总方差的增加而增大。

The scale dependence of dispersivity in multi-facies heterogeneous sediments

Based on a general global covariance function of log conductivity in multi-facies sediments,we developed the macrodispersion coefficient equations for the solute transport in three-dimensional domain.Then we derived the longitudinal dispersivity to show the scale dependence of this parameter.With an example,the time evolution trends and the relative contributions of the auto-and cross-facies transition terms to the macrodispersion have been discussed.Sensitivity analysis indicates that the values of the longitudinal dispersion coefficient are positively correlated to facies mean length and the difference of the mean log conductivity between different facies.The longitudinal dispersivity coefficient also shows clearly a linear dependence on the global variance of the log conductivity in the multi-facies sediments.