Acidizing oil wells

Claim 1

IN A METHOD OF ACIDIZING AN OIL-PRODUCING FORMATION PENETRATED BY A WELL IN WHICH METHOD AN AQUEOUS SOLUTION OF AN ACID IS INJECTED DOWN SAID WELL AND INTO SAID FORMATION, THE IMPROVEMENT COMPRISING EMPLOYING AS THE ACIDIZING AGENT AN AQUEOUS ACID SOLUTION CONTAINING A POLYESTER AND A QUATERNARY AMMONIUM COMPOUND, THE WEIGHT OF QUATERNARY AMMONIUM COMPOUND BEING FROM ABOUT 1 TO 3 TIMES THE WEIGHT OF POLYESTER, THE COMBINED CONCENTRATIONS OF POLYESTER AND QUATERNARY AMMONIUM COMPOUND BEING FROM ABOUT 1 TO ABOUT 0.4 PERCENT BY VOLUME OF SAID ACID SOLUTION, SAID QUATERNARY AMMONIUM COMPOUND BEING SELECTED FROM THE GROUP CONSISTING OF DIMETHYL DICOCO AMMONIUM CHLORIDE AND DIHYDROXYETHYL COCO BENZYL AMMONIUM CHLORIDE, SAID POLYESTER BEING THE REACTION PRODUCT OF TRIMELLITIC ACID, A POLYALKYLENE GLYCOL, A DICARBOXYLIC ACID HAVING A MOLECULAR WEIGHT BETWEEN ABOUT 115 AND ABOUT 730 AND A DETERGENT-FORMING MONOCARBOXYLIC ACID HAVING A HYDROCARBON RADICAL CONTAINING FROM ABOUT 12 TO ABOUT 24 CARBON ATOMS IN THE RADICAL, THE RATIO OF MOLES OF TRIMELLITIC ACID TO DICARBOXYLIC ACID BEING FROM ABOUT 1:1 TO ABOUT 2:1, THE MOLES OF THE POLYALKYLENE GLYCOL BEING EQUAL TO THE MOLES OF DICARBOXYLIC ACID PLUS FROM ABOUT 5/3 TO ABOUT 2-1/2 TIMES THE MOLES OF TRIMELLITIC ACID, THE MOLES OF DETERGENT-FORMING ACID BEING SUFFICIENT TO REACT WITH FROM ABOUT 1/3 TO ALL THE FREE HYDROXYL RADICALS REMAINING AGTER REACTION OF THE POLYALKYLENE GLYCOL WITH THE TRIMELLITIC AND DICARBOXYLIC ACIDS, SAID POLYALKYLENE GLYCOL BEING SELECTED FROM THE GROUP CONSISTING OF POLYETHYLENE GLYCOL HAVING A MOLECULAR WEIGHT FROM ABOUT 200 TO ABOUT 2,000, POLYPROPYLENE GLYCOL HAVING A MOLECULAR WEIGHT FROM ABOUT 1,000 TO ABOUT 5,000 AND POLYMERS OF BOTH ETHYLENE OXIDE AND PROPYLENE OXIDE HAVING A MOLECULAR WEIGHT FROM ABOUT 200 TO ABOUT 5,000.