Numerical simulation of non-isothermal multiphase tracer transport in heterogeneous fractured porous media

We have developed a new numerical method for modeling tracer and radionuclide transport through heterogeneous fractured rocks in a non-isothermal multiphase system. The model formulation incorporates a full hydrodynamic dispersion tensor, based on three-dimensional velocity ®elds with a regular or irregular grid in a heterogeneous geological medium. Two di€erent weighting schemes are proposed for spatial interpolation of three-dimensional velocity ®elds and concentration gradients to evaluate the mass ̄ux by dispersion and di€usion of a tracer or radionuclide. The fracture±matrix interactions are handled using a dual-continua approach, such as the doubleor multiple-porosity, or dual-permeability. This new method has been implemented into a multidimensional numerical code to simulate processes of tracer or radionuclide transport in non-isothermal, three-dimensional, multiphase, porous/fractured subsurface systems. We have veri®ed this new transport-modeling approach by comparing its results to the analytical solution of a parallel-fracture transport problem. In addition, we use published laboratory results and the particletracking scheme to further validate the model. Finally, we present two examples of ®eld applications to demonstrate the use of the proposed methodology for modeling tracer and radionuclide transport in unsaturated fractured rocks. Ó 2000 Elsevier Science Ltd. All rights reserved.