The need for new forms of energy, and in particular the need for renewable and clean ones, led to develompment of Enanched Geothermal Systems, where the well designed stimulation of a geothermal reservoir is the key parameter for the safe development of this technology. Understanding the role that injected fluid properties, in particular viscosity, play on fault reactivation and induced seismicity is fondamental. During this Ph.D. we will apply experimental methods at laboratory scale to aim at recreate the conditions of a silicate bearing-fault under EGS conditions of stress and pore pressure. All the seismic cycle will be investigated, from the nucleation to the propagation of an earthquake. In particular, two type of laoding will be investigate in presence of different fluid: (1) imposing the propagation slip velocity, (2) loading the fault in critical conditions of stress and injecting the fluid directly on the fault. This study will shed light on influence of the fluid on fault stability and reactivation during fluid induced events but also in natural earthquake where fluid pressure is involved.