Abstract: Method for determining the equivalent fracture permeability of a fracture network in a subsurface multi-layered medium from a known representation of this network. The equivalent fracture permeability of a fractured network in a subsurface multi-layered medium, is determined by discretizing with a specific procedure each fracture (F) of the fracture network in fracture elements (R) (such as rectangles for example) and defining nodes N representing interconnected fracture elements in each layer of the medium and determining fluid flows (steady-state flows e.g.) through the discretized network while imposing boundary pressure conditions and fluid transmissivities to each couple of neighboring nodes. The method allows for a systematic linking of fractured reservoir characterization models with dual-porosity simulators in order to create a more realistic modeling of a fractured subsurface geological structure.