Method of acidizing subterranean formations

Claim 1

A method of fracturing a subterranean formation which comprises injecting into said formation at a pressure sufficient to form a fracture therein an acid emulsion comprising a major volume proportion of a hydrocarbon liquid as the internal phase and a minor volume proportion of an aqueous acid solution as the external phase, said acid emulsion containing an effective amount of a fluid loss additive comprising finely divided particulate material present in a concentration of at least 2 pounds per barrel of said emulsion; and from about 1 to about 5 weight percent in said acid solution of a polymer mixture of (a) a vinyl polymer for increasing the viscosity of said aqueous acid solution and selected from the group consisting of polyvinyl alcohol, polyvinyl pyrrolidone, and copolymers of vinyl alcohol and vinyl pyrrolidone, and (b) a water-soluble natural gum, said natural gum constituting at least 25 weight percent of said polymer mixture.

Claim 2

A method of fracturing a subterranean formation which comprises injecting into said formation at a pressure sufficient to form a fracture therein an acid emulsion comprising a major volume proportion of a hydrocarbon liquid as the internal phase and a minor volume proportion of an aqueous acid solution as the external phase, said acid emulsion containing an effective amount of a fluid loss additive comprising finely divided particulate material present in a concentration of at least 2 pounds per barrel of said emulsion; and from about 1 to about 5 weight percent in said acid solution of a polymer mixture of (a) a vinyl polymer for increasing the viscosity of said aqueous acid solution and selected from the group consisting of polyvinyl alcohol, polyvinyl pyrrolidone, and copolymers of vinyl alcohol and vinyl pyrrolidone, and (b) a water-soluble natural gum, said natural gum constituting at least 25 weight percent of said polymer mixture.

Claim 11

A method of fracturing a subterranean formation containing calcareous constituents which comprises injecting into said formation at a pressure sufficient to form a fracture therein an emulsion comprising from about 50 to about 80 volume percent of a hydrocarbon liquid as the internal phase and from about 20 to 50 volume percent of an aqueous liquid as the external phase, said aqueous liquid containing a polymeric thickening agent; and thereafter injecting into said formation an acid emulsion comprising from about 50 to about 80 volume percent of a hydrocarbon liquid as the internal phase and from about 20 to about 50 volume percent of an aqueous acid solution having dispersed therein a fluid loss additive comprising (a) finely divided particulate material present in a concentration of at least 2 pounds per barrel of said acid emulsion, and (b) a water-soluble polymer mixture including a water-soluble natural gum, and a vinyl polymer selected from the group consisting of polyvinyl alcohol, polyvinyl pyrrolidone, and copolymers of vinyl alcohol and vinyl pyrrolidone, the concentration of the vinyl polymer being sufficient to substantially increase the viscosity of the acid solution, and the concentration of the polymer mixture in the aqueous acid solution being at least one weight percent and said natural gum comprises at least 25 weight percent of said polymer mixture.

Claim 12

A method of fracturing a subterranean formation containing calcareous constituents which comprises injecting into said formation at a pressure sufficient to form a fracture therein an emulsion comprising from about 50 to about 80 volume percent of a hydrocarbon liquid as the internal phase and from about 20 to 50 volume percent of an aqueous liquid as the external phase, said aqueous liquid containing a polymeric thickening agent; and thereafter injecting into said formation an acid emulsion comprising from about 50 to about 80 volume percent of a hydrocarbon liquid as the internal phase and from about 20 to about 50 volume percent of an aqueous acid solution having dispersed therein a fluid loss additive comprising (a) finely divided particulate material present in a concentration of at least 2 pounds per barrel of said acid emulsion, and (b) a water-soluble polymer mixture including a water-soluble natural gum, and a vinyl polymer selected from the group consisting of polyvinyl alcohol, polyvinyl pyrrolidone, and copolymers of vinyl alcohol and vinyl pyrrolidone, the concentration of the vinyl polymer being sufficient to substantially increase the viscosity of the acid solution, and the concentration of the polymer mixture in the aqueous acid solution being at least one weight percent and said natural gum comprises at least 25 weight percent of said polymer mixture.