Abstract: When sulfonated surfactants are used to displace crude oil from a subterranean formation, the produced oil and water contain the surfactant and form a tight emulsion. This crude oil-water-surfactant emulsion is broken with a strong inorganic acid, for example, hydrochloric acid. The amount of acid added is sufficient to lower the pH of the water in the emulsion to 3.0 or lower. Thereafter, the oil is separated from the emulsion by conventional techniques.

Abstract: An enhanced oil recovery process comprises injection of water into a subterranean formation followed by the injection of a surfactant such as a micellar fluid and a thickening agent such as a polymer solution to drive oil toward a production well. Temperatures and pressures of injection of the water, surfactant, and thickening agent are controlled so as to thermoelastically fracture the formation behind the oil-water bank to increase the injectivity rate and propagation rate of the slugs of fluids behind the oil-water bank to control the shape of the flood front and to minimize misdirected fracturing ahead of the flood front.

Abstract: The effective permeability of subterranean hydrocarbon bearing formations with respect to surfactant and drive fluid injection processes is enhanced by preceding the surfactant fluid injection step with creation of multiple formation fractures using tailored pressure pulses produced by gas generating propellant canisters disposed in the injection well. Fluid injectivity rates are increased by subsequent fracture extensions provided by repeated steps of generating high pressure gas pulses at selected intervals.