title: Signature of non-Fickian solute transport in complex heterogeneous porous media.
abstract: We simulate transport of a solute through three-dimensional images of different rock samples, with resolutions of a few microns, representing geological media of increasing pore-scale complexity: a sandpack, a Berea sandstone, and a Portland limestone. We predict the propagators (concentration as a function of distance) measured on similar cores in nuclear magnetic resonance experiments and the dispersion coefficient as a function of Péclet number and time. The behavior is explained using continuous time random walks with a truncated power-law distribution of travel times: transport is qualitatively different for the complex limestone compared to the sandstone or sandpack, with long tailing, an almost immobile peak concentration, and a very slow approach to asymptotic dispersion.
authors.affiliation: Department of Earth Science and Engineering, Imperial College London, United Kingdom. b.bijeljic@imperial.ac.uk
authors.forename: Branko
authors.initials: B
authors.lastname: Bijeljic
authors.forename: Peyman
authors.initials: P
authors.lastname: Mostaghimi
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Blunt