Effects of Using a Continuum Representation to Simulate Discrete Fracture Networks

Abstract

The substitution of matrix or continuum permeability for discrete fracture systems requires a radically different treatment of transport in the matrix. The spatial distribution of pressure is reasonably well described by inclusion of only the major fractures. Transport of tracer and heat, however, depends on a detailed knowledge of fluid velocities. Two factors are involved. First, the velocities are dependant on the active porosity of the system. Because fractures channel flow, the active porosity may be much smaller that the total porosity of the system. Secondly, the distribution of velocities is generally not normally distributed precluding the use of a Gaussian dispersion model. Characterization of the active porosity and velocity distribution are necessary to quantify tracer and heat movement.