| abstract |
Viscoelastic surfactant fluids, and methods of using such fluids and controlling the viscosity thereof. In one embodiment, the present invention provides a viscoelastic surfactant fluid comprising an aqueous-base fluid, a surfactant, and a metal ion having at least two oxidation states wherein at least one of the oxidation states interferes with the ability of the surfactant to form a viscosifying micelle. |