Models of Fracture-Matrix Interactions During Multiphase Heat and Mass Flow in Unsaturated Fractured Porous Media

Abstract

Abstract Models of liquid, gas, and heat flow between fractures and matrix elements in dual-permeability models are presented in this paper. Heterogeneities necessitate scaling the liquid geometric conductance between fracture and matrix elements to account for a reduction in the wetted area available for liquid flow while maintaining reasonable conductances for gas and heat flows. The models in this study consisted of conductance multipliers that were either constant, a function of upstream saturation, or a function of upstream relative permeability. Numerical analyses were performed using TOUGH2 to determine hydrologic and thermal parameters that are sensitive to the various fracture-matrix models. Results showed that for thermohydrologic simulations of the potential repository at Yucca Mountain, the ambient hydrology (e.g., matrix liquid saturations and fracture liquid flow) was strongly dependent on the fracture-matrix interaction model. The thermal response of the system was less sensitive to the different fracture-matrix models in the dual-permeability systems.