Radial Dispersion in a Double-Porosity System with Fracture Skin

Abstract

The problem of dispersion, advection and adsorption of a tracer in a double-porosity reservoir due to tracer injection in a well with a steady, radially divergent flow field was solved for the case of constant tracer concentration in the injection well. Longitudinal dispersion and advection was assumed to dominate transport in the fracture system and tracer diffusion and adsorption klas assumed to dominate movement of the tracer in the matrix blocks. The blocks were assumed to be sphere shaped and covered with a thin skin of material that provides resistance to the diffusion of tracer into the blocks. Values of dimensionless concentration in the fracture system versus dimensionless time were computed by numerical inversion of the Laplace transform solution to the Airy equation. Type curves demonstrate effects of changing reservior characteristics and show the usefulness of the concept of fracture skin in understanding dispersive processes in fractured porous media.