Abstract:

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.

Key words: dispersivity, multifacies heterogeneous sediments, scale dependence, macrodispersion coefficient equations