ACCURACY AND EFFICIENCY OF A SEMIANALYTICAL DUAL-POROSITY SIMULATOR FOR FLOW IN UNSATURATED FRACTURED ROCK MASSES

A semi-analytical dual-porosity simulator for unsaturated flow in frac tured rock masses has been developed. Fluid flow between the fracture network and the matrix blocks is described by analytical expressions t hat have been derived from approximate solutions to the imbibition equ ation. These expressions have been programmed into an unsaturated flow simulator, TOUGH, as a source/sink term. Flow processes are then simu lated using only fracture elements in the computational grid. The modi fied code is used to simulate flow along single fractures, and infiltr ation into pervasively fractured formations. Comparisons are made with simulations carried out using discretization of both the fractures an d matrix blocks. The new semi-analytical code is shown to be accurate, and typically requires an order of magnitude less computational time.