Enhanced transport with early arrivals and reduced attenuation in ensemble realisations of discrete fracture networks with internal fracture heterogeneity

Abstract Multiple realisations of a 100 × 100 × 100 m 3 rock volume with stochastically generated fractures based on statistics collected from the Forsmark site in Sweden are studied using different texture representations of internal fracture heterogeneity. Solute transport by particle tracking is investigated with reference to a smooth fracture plane representation, corresponding to an assumption of effectively homogenous fractures. A Lagrangian transport formulation is adopted where the two key transport variables, travel time τ and transport resistance β , are evaluated. Results indicate that fracture heterogeneity textures with strong internal correlation lead to an increased number of particles with short arrival times and weak transport resistance. This combined effect can lead to a reduction in contaminant attenuation for solute transport in discrete fracture networks when compared to homogeneous fracture property assumptions. A need for the quantification of internal fracture heterogeneity of natural fractures is thereby identified in order to further evaluate implications for real-world applications.