Hydrodynamic characterisation of real fracture systems is necessary to improve modelling of fracture reservoirs as well as nuclear waste disposal sites. This characterisation is usually considered globally and theoretically but very few studies have aimed to identify the real physical environment of flow (matrix, faults, joints etc.) before establishing hydrodynamical models. We present a case study in a fractured reservoir aiming to give an example of how and why fluids actually flow within a given fracture at the various scales of fracturation of a fracture network. This study demonstrates that the determination of type and orientation of fractures actually supporting flow is necessary for accurate interpretation of the pumping tests within a fractured reservoir. It also shows that there is no simple relationship between the fault offset and the importance of flow, probably due to the influence of in situ stress. It is shown that the combination of various methods can be used to determine the fracture-flow relationship and behaviour at subseismic scale in subsurface conditions.