Transient dual-porosity simulations of unsaturated flow in fractured rocks
This report describes the development and use of a semi-analytical dual-porosity simulator for unsaturated flow in fractured rock masses. Fluid flow between the fracture network and the matrix blocks is described by a nonlinear equation that relates the imbibition rate to the local difference in liquid-phase pressure between the fractures and the matrix blocks. This equation is a generalization of the Warren-Root equation, but is accurate in both early and late time regimes. The fracture/matrix interflow equation has been incorporated into a computational module that acts as a source/sink term for fracture elements; this module is compatible with the unsaturated flow simulator TOUGH. Flow processes are then simulated using only fracture elements in the computational grid. This semi-analytical dual-porosity module has been tested with TOUGH on various problems involving transient flow in fractured/porous media, and compared with simulations performed using explicit discretization of the matrix blocks. The new semi-analytical dual-porosity model accurately simulates flow processes in unsaturated fractured rocks, and typically requires an order of magnitude less computational time than do simulations using fully-discretized matrix blocks.
- Research Organization:
- Lawrence Berkeley Lab., CA (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 70743
- Report Number(s):
- LBL--36807; ON: DE95012438
- Country of Publication:
- United States
- Language:
- English
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