A look at dispersion in porous media through computed tomography imaging

This paper presents a method for measuring the longitudinal dispersion coefficient and the adsorption properties of porous media by X-ray computed tomography (CT) imaging. The in situ solvent concentration profiles of tracer tests were imaged and fitted to a convection-dispersion mathematical model. In addition to providing the average dispersion coefficient traditionally measured with breakthrough curves, our method allows the dispersion phenomenon to be visualized and the contribution of heterogeneity to the dispersion coefficient to be estimated. The method is demonstrated by measuring the dispersion coefficients and adsorption properties of a sandpack and a Berea sandstone. Results show that heterogeneity increases the dispersion coefficient above that of a homogeneous porous medium. Adsorption was found to be higher in the Berea sandstone, a natural porous medium, than in the clean sandpack. CT imaging of the tracer tests has shed more light on the dispersion and adsorption phenomena in porous media.