Oxidative internal breaker system with breaking activators for viscoelastic surfactant fluids

摘要

Compositions and methods are given for delayed breaking of viscoelastic surfactant gels inside formation pores, particularly for use in hydraulic fracturing. Breaking inside formation pores is accomplished without mechanical intervention or use of a second fluid. Bromate oxidizing agents are used along with selected breaking activators for the bromate breaking compounds. Useful bromate breaking activators include acid-generating breaking activators, oxidizing sulfur containing breaking activators, and reducing agent breaking activators.

主权项

1. A method of treating a subterranean formation penetrated by a wellbore comprising a) injecting into the pores of the formation an aqueous gel comprising a non-polymeric viscosifier, a bromate oxidizing agent soluble in the gel, and a breaking activator for said bromate oxidizing agent, and b) allowing said gel to lose viscosity in the pores after the injection
wherein said breaking activator is selected from the group consisting of sodium thiosulfate, glutaraldehyde, sodium persulfate, sodium tetrathionate, glucose, sodium bisulfite, and sodium metabisulfite; and wherein the aqueous gel exhibits a decrease in viscosity at temperatures lower than exhibited in the absence of a breaking activator.