Spatial Moment Analysis for Transport of Nonreactive Solutes in Fracture-Matrix System

Abstract

This paper presents an analysis using spatial moments for transport of nonreactive solutes in a single fracture-matrix system using a dual porosity framework. The velocity and dispersion obtained using the first and second spatial moments are found to have two regimes. The effect of fracture velocity, fracture dispersivity, fracture spacing, matrix diffusion coefficient, and matrix porosity on both regimes are analyzed. The first regime is characterized by a behavior wherein both velocity and dispersion are functions of time and all of the above parameters of the fracture-matrix system are found to have an influence. In the second regime, they are independent of time similar to the behavior of conservative solutes in an ideal porous media. This regime is characterized by the influence of a few parameters of the fracture-matrix system. The empirical relationships for solute velocity, macrodispersion coefficient, and dispersivity in the asymptotic stage are presented.