Dualpermeability

Dual-permeability is a modeling concept used to describe flow and transport in porous media that contain two distinct, interconnected pore networks, typically fractures and the surrounding matrix. In a dual-permeability framework, the fracture network and the matrix are treated as separate continua, each with its own porosity and permeability, and a transfer term governs exchange of fluids and dissolved substances between them.

Mathematically, this approach yields two coupled mass-balance equations, one for the fractures and one for the matrix. Each equation resembles a porous-media flow equation but uses network-specific properties. The exchange term, often proportional to the pressure difference or concentration difference and to an interfacial area, captures matrix-fracture interaction such as diffusion into the matrix blocks or drainage from fractures into the matrix.

The model is used to simulate groundwater flow and transport in fractured rocks and soils with macropores, as well as in fractured petroleum reservoirs and geothermal systems. It is also employed in studies of nuclear-waste isolation where rapid flow occurs in fractures while the matrix provides storage.

Parameter estimation for porosity, permeability, and transfer rates can be challenging and typically requires field data, laboratory experiments, or calibration against observed hydraulic responses.

Compared with dual-porosity models, dual-permeability allows meaningful flow within both networks, though fracture flow often dominates. The approach is implemented in numerical simulators to improve predictions of breakthrough curves, residence times, and contaminant migration in complex fractured media.