Sealing porous structures

Claim 1

IN A PROCESS FOR SEALING A PERMEABLE STRATUM IN A WELL BORE, THE STEPS WHICH COMPRISE INTRODUCING INTO THE WELL BORE A MIXTURE OF A LIQUID PHENOL-FORMALDEHYDE RESIN, A PHENOL-RESORCINOLFORMALDEHYDE RESIN AND FROM 2-10% OF A FORMALDEHYDE-GENERATING SUBSTANCE TAKEN FROM THE GROUP CONSISTING OF HEXAMETHYLENE TETRAMINE, PARAFORMALDEHYDE AND TRIOXYMETHYLENE, SAID MIXTURE CONTAINING SAID RESINS IN SUCH RELATIVE PROPORTIONS AS TO PRODUCE A COMBINED RESORCINOLPHENOL RATION BETWEEN 25:100 AND 45:100, FORCING SAID MIXTURE INTO THE PERMEABLE STRATUM AND ALLOWING THE RESIN TO CURE TO AN INFUSIBLE, INSOLUBLE STATE, SAID LIQUID PHENOL-FORMALDEHYDE RESIN CONTAINING 2-3 MOLS OF COMBINED FORMALDEHYDE FOR EACH MOL OF PHENOL AND HAVING BEEN MADE UNDER ALKALINE CONDITIONS AND THEN ACIDIFIED TO A PH OF 4.5-7, AND SAID PHENOL-RESORCINOL-FORMALDEHYDE RESIN CONTAINING 1-1.5 MOLS OF COMBINED FORMALDEHYDE FOR EACH MOL OF PHENOL AND 40-90 PARTS OF COMBINED RESORCINOL FOR EVERY 100 PARTS OF PHENOL AND HAVING BEEN MADE BY PARTIALLY REACTING PHENOL AND FORMALDEHYDE UNDER ALKALINE CONDITIONS, REACTING RESORCINOL WITH THE PARTIAL CONDENSATION PRODUCT UNDER ALKALINE CONDITIONS UNTIL A VISCOSITY OF 25-100 CENTIPOISES AT 25*C. IS ATTAINED AND THEN DEHYDRATING THE PHENOL-RESORCINOL-FORMALDEHYDE CONDENSATION PRODUCT TO A WATER CONTENT OF 5-12% AND A VISCOSITY OF NOT OVER 8000 CENTIPOISES AT 25*C., SAID VISCOSITY BEING MEASURED IN A SOLUTION CONTAINING 20 PARTS OF ETHANOL PER 100 PARTS OF PHENOL ORIGINALLY REACTED.