A method for inhibiting water permeation in an extraction well of a hydrocarbon fluid from an underground reservoir containing: supplying a water-in-oil emulsion an oily continuous phase and an aqueous discontinuous phase containing a plurality of particles of at least one hydrogel containing a cationic polymer; and positioning the water-in-oil emulsion in contact with the underground reservoir. The present invention also concerns a treatment fluid for hydrocarbon fluid extraction wells containing the aforementioned water-in-oil emulsion and the related preparation process.