A process for the treatment of a rock formation or cavity, including the step of injecting, into the rock formation or cavity, a water solution of a water-soluble thermo-thickening polymer, the thermo-thickening polymer being able to form a gel at a threshold temperature (Tg), an inner temperature (Tint) of the rock formation or cavity being equal or superior to the threshold temperature (Tg), the process being characterized in that the thermo-thickening polymer is a cellulose chain, partially etherified with C1-C6 alkyl or hydroxyalkyl groups, or a polyacrylamide-based copolymer including N-isopropylacrylamide and/or N-vinylpyrrolidone groups. Such a process is advantageous for water shutoff in gas- or oilfields, or to solve to water channelling problems between injection wells and production wells.