The proposed model is based on the general idea, that flow and advective transport in stimulated HDR reservoirs occur mainly in fractures, whose orientation is linked by the tectonic stress field. Therefore, a deterministic fracture network model is established which represents the mean geometrical features of a stimulated HDR system. A physical and mathematical model of a fractured porous medium is developed for describing flow and transport within the interacting system of fractures and rock matrix. The model is then translated into a discrete finite-element approach.