Abstract: Subterranean formations at temperatures above 250.degree. F. are acidized by introducing a solution of a halogenated hydrocarbon and an organic solvent and allowing the halogenated hydrocarbon to hydrolyze in an aqueous medium to form a hydrohalic acid. Corrosion of metals, e.g., well casing, is inhibited by the presence of the solvent. The acidizing solution can be introduced as a liquid or as a mist in a substantially anhydrous gas. The aqueous medium can be naturally present in the formation or can be introduced into the formation as a liquid or as a foam simultaneously with the acidizing solution.

Abstract: The permeability of high-temperature subterranean hydrocarbon-producing reservoirs is increased by introducing therein a mixture containing a tertiary carboxylic acid alkylated amide, an aqueous solution of an acid or acids, and a water-soluble polymer, preferably a nitrogen-containing polymer.

Abstract: The permeability of subterranean hydrocarbon-producing reservoirs is increased by introducing therein a mixture containing a tertiary carboxylic acid alkylated amide and a glycol ether in combination with an aqueous solution of an acid and, optionally, including a water-soluble polymer, preferably a nitrogen-containing polymer.

Abstract: Subterranean reservoirs having temperatures above about 250.degree. F. are acidized by atomizing an acid precursor in an anhydrous gas to form a mist, mixing the mist with water in the borehole of a well penetrating the reservoir to form a treating fluid comprising a dispersion of fine particles of acid precursor and anhydrous gas in water, and injecting the treating fluid into the reservoir. The acid precursors are normally liquid halogenated hydrocarbons which hydrolyze in the presence of water to generate a hydrohalic acid.

Abstract: A method for treating a hot water-containing fluid stream passing through a conduit, under conditions of temperature and pressure whereupon at least a portion of the water flashes to steam, to inhibit the formation of scale deposited on the conduit and/or dissolve any such scale already formed, and to inhibit corrosion of the conduit wherein there is added to the fluid stream an effective amount of a solution of a water-soluble compound which provides a nitrogen-containing cation capable of flashing to become a gas at high temperatures selected from the group consisting of ammonium halides, ammonium salts of inorganic acids, ammonium salts of organic acids, ammonium salts of alpha hydroxy organic acids, quaternary ammonium halides, quaternary ammonium salts of inorganic acids, quaternary ammonium salts of organic acids, amine salts of inorganic acids, amine salts of organic acids and amides. Optionally the solution or dispersion also contains a water-soluble or dispersible polymer and/or a buffering agent.

Abstract: A method for inhibiting the dissolution of silica from the matrix around a well during injection of steam into the matrix by adding to the feedwater used to generate the steam or the steam itself an inhibitor comprising an ammonium or substituted ammonium compound selected from the group consisting of ammonium halides, ammonium salts of inorganic acids, ammonium salts of carboxylic acids, quaternary ammonium halides, and amine or substituted amine hydrochlorides.

Abstract: A method for conditioning a flow of hot geothermal brine or aqueous liquid to reduce scale formation by pH-sensitive, dissolved materials includes injecting into the flow of brine or liquid an anhydrous, halogenated acid precursor which hydrolyzes in the brine or liquid to form a hydrohalic acid. The acid precursor, which may be tetrachloromethane, is preferably injected into an extraction well at the vicinity of the producing formation at a rate reducing the pH of the brine or liquid about one pH unit, or to about 3.5, near the injection point. The method also provides for increasing, if necessary, the acid precursor hydrolysis rate in the brine or liquid by atomizing the injected acid precursor with a pressurized fluid, preferably gaseous nitrogen.

Abstract: Subterranean formations having temperatures above about 250.degree. F. are acidized by introducing a substantially anhydrous foamed treating fluid through a well and into the formation. The treating fluid contains a gas, a nonionic substantially hydrophobic foaming agent and an acid precursor which is normally liquid halogenated hydrocarbon having one or two carbon atoms per molecule. The acid precursor hydrolyzes in situ to generate a hydrohalic acid.

Abstract: The less permeable zones of subterranean formations having temperatures above about 250.degree. F. are acidized by selectively plugging the more permeable zones with acid-soluble particulate diverting agents and then injecting a substantially anhydrous acid precursor into the formation. The acid precursor, which is a normally liquid halogenated hydrocarbon having one or two carbon atoms per molecule, hydrolyzes in situ to generate a hydrohalic acid. Subsequent to the placement of the acid precursor in the less permeable zones, the diverting agents may be solubilized in acid, such as the partially spent acid returning to the well.

Abstract: An aqueous fluoride salt solution and a substantially anhydrous acid precursor are introduced through a well into a high temperature subterranean formation containing siliceous materials. The acid precursor, which is a normally liquid halogenated hydrocarbon having one or two carbon atoms, hydrolyzes in situ to generate a hydrohalic acid which combines with the fluoride salt to acidize the siliceous materials.

Abstract: Subterranean formations having temperatures between about 250.degree. F. and about 700.degree. F. are acidized by introducing a substantially anhydrous acid precursor through a well and into the formation, wherein the precursor hydrolyzes in situ to generate a hydrohalic acid. The acid precursor is a normally liquid, halogenated hydrocarbon having one or two carbon atoms per molecule which is thermally stable under the high temperature and pressure conditions encountered prior to hydrolysis.