A fully electric downhole safety tool comprising a valve for flow blockage in oil and gas wells completion operations under emergency conditions is described. Valve comprises an actuation array constituted by a hollow shaft motor, nut, spindle and sliding sleeve, so that upon starting, the opening movement of said array compresses a valve closure spring and places the flapper sealing in the open position, enabling communication to occur between zones and fluid to flow. To close the valve, as soon as the electrical supply is ceased, the string relaxes, the sliding sleeve, under spring force, returns as is the case for the whole of the actuation array, and flapper sealing is exposed to the flow so that valve returns to the closed position, physically blocking the flow.