The economic production from shale gas reservoir depends on the success of hydraulic stimulation, which is aimed at the creation of a permeable complex fracture network. This is achieved by the reactivation of a natural fracture network; however, the reactivation may be accompanied by unwanted seismicity. Coupled modelling is required to completely describe the physical processes involved. We developed a model using FLAC3D, by implementing in it gas-flow, dynamic permeability changes and the development of seismic events during fracture reactivation. The geomechanical and the flow behaviour of the fracture were implemented using effective continuum parameters. For the activation of a fracture zone, we used the ubiquitous joint model available in FLAC3D. Fracture deformations are the result of both reversible tensile and irreversible shear deformations. Models with different numbers of fracture sets, parallel or intersecting, were developed and simulated. With our approach we can simulate and visualize fracture reactivation, permeability enhancement and the location and size of induced seismic events.