Aqueous gels for plugging fractures in subterranean formation and production of said aqueous gels

A method for producing an aqueous gel having increased gel strength, and which is suitable for plugging fractures in subterranean formations, which method comprises:

• thickening water by incorporating therein a thickening amount of a water-soluble cellulose ether;
• incorporating in said water a water-soluble compound of a polyvalent metal, wherein the valence state of the metal therein is capable of being reduced to a lower polyvalent valence state, in an amount which is sufficient to cause gelation of said water containing said cellulose ether when the valence of at least a portion of said metal is reduced to said lower valence state;
• incorporating in said water a water-soluble reducing agent in an amount which is effective to reduced at least a portion of said metal to said lower valence state and cause said gelation with the formation of said gel, said reducing agent being selected from the group consisting of sodium sulfite, sodium hydrosulfite, potassium hydrosulfite, sodium metabisulfite, potassium sulfite, sodium bisulfite, potassium metabisulfite, sodium sulfide, hydrogen sulfide, sodium thiosulfate, potassium thiosulfate, thioacetamide, hydroquinone, p-hydrazinobenzoic acid, hydrazine phosphite, hydrazine dichloride, and mixtures thereof;
• and
• incorporating in said water a finely divided solid capable of causing, and in an amount thereof sufficient to cause, an increase in the gel strength of said gel.