Particle-tracking simulations of anomalous transport in hierarchically fractured rocks

Complex topology of fracture networks and interactions between transport processes in a fracture and the ambient un-fractured rock (matrix) combine to render modeling solute transport in fractured media a challenge. Classical approaches rely on both strong assumptions of either limited or full diffusion of solutes in the matrix and simplified fracture configurations. We analyze fracture-matrix transport in two-dimensional Sierpinski lattice structures, which display a wide range of matrix block sizes. The analysis is conducted in several transport regimes that are limited by either diffusion or block sizes. Our simulation results can be used to validate the simplifying assumptions that underpin classical analytical solutions and to benchmark other numerical methods. They also demonstrate that both hydraulic and structural properties of fractured rocks control the residence time distribution.

► Fracture-matrix transport simulations in two-dimensional Sierpinski lattice structures. ► Our analysis is conducted for several transport (and diffusion) regimes. ► It improves previous studies that are usually limited to idealized systems. ► Study of classical simplifying assumptions and benchmarking of numerical methods. ► Quantification of hydraulic and structural properties' effects on solute behavior.