A method for controlling the permeability of an oil well includes the steps of preparing a polymerizable bicomponent system having at least a fluid with at least an olefinically unsaturated first polymerizable compound; optionally, at least one radical polymerization initiator IA, the initiator IA being activated thermally or in the presence of an accelerating compound and a fluid with a radical polymerization activator, the activator being selected from: a radical polymerization initiator IB for polymerizing the polymerizable compound, the initiator IB having an activation temperature equal to or lower than the temperature of the thief zone, an accelerator of the initiator IA, The method further includes injecting one of the fluids into the well annulus until the thief zone is reached, and injecting the remainder into the tubular element, until it comes into contact with the fluid injected through the annulus to form a blocking polymer at the thief zone.