The present invention relates to a method for inhibiting water permeation in an extraction well of a hydrocarbon oil from an underground reservoir which comprises injecting into said reservoir at least one polymerizable composition comprising: at least one hydrophilic monomer, -at least one hydrophilic initiator of radical polymerization with thermal activation (hydrophilic initiator), at least one lipophilic initiator of radical polymerization with thermal activation (lipophilic initiator). The present invention also relates to the polymerizable compositions that can be used in said method.