Abstract: The present invention provides low viscosity acid-in-oil emulsions, surfactant systems and methods of using the emulsions and surfactants for stimulating the production of hydrocarbons from subterranean producing formations. The low viscosity acid-in-oil emulsions are basically comprised of a hydrocarbon oil forming the external phase of the emulsion, an emulsifying agent of a type which forms and stabilizes an acid-in-oil emulsion, an emulsion viscosity reducing agent comprising a fatty ammonium salt of a fatty acid and an aqueous acid solution forming the internal phase of the emulsion.

Abstract: The present invention provides low viscosity acid-in-oil emulsions, surfactant systems and methods of using the emulsions and surfactants for stimulating the production of hydrocarbons from subterranean producing formations. The low viscosity acid-in-oil emulsions are basically comprised of a hydrocarbon oil forming the external phase of the emulsion, an emulsifying agent of a type which forms and stabilizes an acid-in-oil emulsion, an emulsion viscosity reducing agent comprising a fatty ammonium salt of a fatty acid and an aqueous acid solution forming the internal phase of the emulsion.

Abstract: Methods of preparing and using a clay stabilizing agent are provided. The agent is prepared by polymerizing diallyldimethylammonium chloride with sulfur dioxide in the presence of a polymerization reaction rate retarder to form a solid cationic copolymer having a high sulfur content. When dissolved in an aqueous carrier fluid, the copolymer is particularly effective in preventing clay swelling and/or fines migration.

Abstract: An anti-sludging agent for enhancing the recovery of sludging oil crudes from hydrocarbon-bearing formations during acid stimulation treatments comprising an admixture of dicyclopentadiene and a mixture of naturally occurring cyclic monoterpenes isolated from Pinus species which is added in at least a sludge-inhibiting amount to the acid used for stimulation.

Abstract: An aqueous gel containing a crosslinking agent comprising an organotitanate chelate and a retarding agent which delays crosslinking of the gel. This retarding agent comprises a polyhydroxyl-containing compound. The gel is useful for fracturing and placing propping agents within a subterranean formation. The gel has a high viscosity in the formation and has pumping characteristics in turbulent flow similar to those of water.