Abstract: There is disclosed a method of treating a subterranean substantially carbonate-free sandstone formation associated with a well completed in said substantially carbonate-free sandstone formation comprising displacing into said formation through said well an effective amount of an acidic aqueous solution comprising from about 5 to about 36 weight % phosphoric acid, from about 0.6 to about 5 weight % of a highly polar surface active agent which is a citric acid-monoethanolamine elimination reaction product, and an effective amount of a ferrous metal corrosion inhibitor. For treating a subterranean limestone or dolomitic formation or a sandstone formation having a substantial carbonate content there is additionally included in the acidic aqueous solution an amount of a phosphate crystal modifying agent sufficient to control crystal growth, minimize crystal agglomeration and minimize crystal adhesion to the formation.

Abstract: There is disclosed a method of treating a subterranean substantially carbonate-free sandstone formation associated with a well completed in said substantially carbonate-free sandstone formation comprising displacing into said formation through said well an effective amount of an acidic aqueous solution comprising from about 5 to about 36 weight % phosphoric acid, from about 0.6 to about 5 weight % of a highly polar surface active agent which is a citric acid-monoethanolamine elimination reaction product, and an effective amount of a ferrous metal corrosion inhibitor. For treating a subterranean limestone or dolomitic formation or a sandstone formation having a substantial carbonate content there is additionally included in the acidic aqueous solution an amount of a phosphate crystal modifying agent sufficient to control crystal growth, minimize crystal agglomeration and minimize crystal adhesion to the formation.