MODELING COUPLED FLUID FLOW AND TRANSPORT PROCESSES IN FRACTURED POROUS MEDIA

Fractured geologic materials are examples of highly heterogeneous systems because of the very large contrast in material properties, such as permeability and specific storage, between the fractures and the surrounding matrix. Heterogeneity in flow and transport properties also exists within single fractures, between the numerous fractures that form a network and within the matrix surrounding the fractures. This high level of spatial variability in flow and transport properties greatly complicates field characterization of fractured systems. It also increases uncertainty in the knowledge of these systems and affects the type of flow and transport model that is applicable. Although great advances in model capabilities have been made in recent years, the development of numerical models to simulate fluid flow and solute transport still remains an active area of research in fractured rock hydrogeology. This talk aims at giving an overview of some current model capabilities and limitations in the context of the control-volume finite element model, FRAC3DVS/HydroGeoSphere. The model can simulate 3D variably-saturated flow, heat and reactive mass transport in fractured porous media using an equivalent porous medium, a dual continuum or a discrete fracture approach. Recent developments have originated from specific application needs and have focused on variable-density fluid flow and reactive transport in discrete fracture networks and dual continuum simulations for variably-saturated flow and transport in fractures and macropores. The limitations associated with fractured rock include the availability of data, the very large computational effort associated with some large-scale simulations that can consider uncertainty in model parameters, the representation of complex 3D fracture networks and the need to add simulation capabilities such as coupled physical and chemical processes. Work is needed to remove these limitations and further improve modeling capabilities for fractured geologic materials. It is also expected that, because increasing attention is given to water resources at the watershed scale, novel applications of fractured rock models will be needed to investigate coupled flow and transport processes at scales different than those previously investigated.