Abstract: An improved method of acidizing sour gas wells involving the injection of an aqueous acidizing solution comprising: water, an acid, an effective amount of an iron complexing agent (e.g., EDTA) capable of stabilizing the ferrous, Fe(II), ion in solution in the presence of H.sub.2 S and an effective amount of an iron reducing agent (e.g., erythorbic acid, ascorbic acid and mixtures thereof) capable of reducing the ferric, Fe(III), ion in solution to ferrous Fe(II), ion at a pH of about 6.0 or less. Such a process is effective in reducing and inhibiting the precipitation of Fe(OH).sub.3, FeS and S in sour wells.

Abstract: The formation and subsequent precipitation of undesirable ferric compounds during the acid treatment of wells is substantially eliminated by incorporating in said treating acid an inhibiting amount of a monobasic alkanoic and/or alkenoic acid having at least four carbon atoms and bearing at least two alcoholic hydroxyl groups per molecule, and/or a soluble salt or .gamma.-lactone of said acid. E.g. ascorbic acid or erythorbic acid.

Abstract: The permeability of siliceous or calcareous subterranean formations adjacent a wellbore is increased by contacting the formation with a gelled aqueous acid capable of dissolving mineral constituents in the formation. The gelled aqueous acid compositions comprise (a) aqueous hydrochloric acid, and (b) a readily soluble gelling agent. Component (b) contains a sufficient amount of a polyoxyethylene glycol to gel the acid and enough ammonium-, alkali-, or alkaline earth metal bicarbonate or carbonate to cause rapid dissolution and dispersion of the polyoxyethylene glycol in the aqueous hydrochloric acid.

Abstract: Aqueous xanthan gums normally crosslink at a pH greater than about 1.5 in the presence of ferric ions. This phenomenon is undesirable under many conditions of use, such as acidizing treatments of wells, and is inhibited or prevented by adding certain soluble alkanoic and/or alkenoic acids to the system. The alkanoic and alkenoic acids have at least 4 carbon atoms and bear at least 2 alcoholic hydroxyl groups per molecule and can be added as the organic acid per se or as a soluble salt or .gamma.-lactone. Ascorbic acid and erythorbic acid are examples.

Abstract: A formation is acidized with a composition comprising a formation acidizing acid and a cationic surfactant which renders oil-containing earthen formations oil-wet, said surfactant being present in said composition in an amount which is sufficient to increase the reaction time of the acid acting on the formation.

Abstract: A subterranean formation (e.g. gas, oil or water bearing formation) is acidized with an emulsion comprising an aqueous acidizing solution, an oil and a cationic surfactant which renders oil-containing earthen formations oil-wet, said surfactant being present in said emulsion in an amount which is sufficient to increase the reaction time of the acid acting on the formation.

Abstract: The present invention relates to a composition and method for the acid stimulation of subterranean formations containing a fluid to be recovered. The composition comprises a mixture of an acid which solubilizes at least a portion of the formation, an alcohol in which said acid and carbon dioxide are soluble, and a small proportion of water and carbon dioxide. In practicing the method the composition is prepared as a liquid mixture, introduced into the formation under pressure, allowed to react with the formation and then the pressure is released to recover spent acid.