Metal-mediated viscosity reduction of fluids gelled with viscoelastic surfactants
AssigneeBaker Hughes Incorporated
InventorJames B. Crews
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Abstract
Fluids viscosified with viscoelastic surfactants (VESs) may have their viscosities reduced (gels broken) by the direct or indirect action of a composition that contains at least one metal ion source and optionally at least one second source. An optional second source may be a chelating agent where at least one reducing agent source may be additionally optionally used. Another optional component with the metal ion source includes a second, different metal ion source. The breaking composition is believed to directly attack the VES itself, possibly by disaggregating or otherwise attacking the micellar structure of the VES-gelled fluid, and/or possibly by changing the chemical structure of the VES to give two or more products.
Claims24
A method for breaking viscosity of aqueous fluids gelled with a viscoelastic surfactant (VES) comprising adding to an aqueous fluid gelled with at least one VES in an amount effective to increase the viscosity of the aqueous fluid, a composition in an amount effective to reduce the viscosity of the gelled aqueous fluid,
- where the composition comprises from about 0.01 to about 300 ppm, based on the total fluid of at least one transition metal ion source, and
- where the VES is selected from the group consisting of amines, amine salts, quaternary ammonium compounds, amine oxides, ethoxylated fatty amines, methyl ester sulfonates, betaines, modified betaines, sulfosuccinates, and mixtures thereof.
An aqueous fluid comprising:
- water;
- at least one viscoelastic surfactant (VES) in an amount effective to increase the viscosity of the aqueous fluid, where the VES is selected from the group consisting of amines, amine salts, quaternary ammonium compounds, amine oxides, ethoxylated fatty amines, methyl ester sulfonates, betaines, modified betaines, sulfosuccinates, and mixtures thereof;
- and
- a composition in an amount from about 0.01 to about 300 ppm based on the total fluid, to reduce the viscosity of the gelled aqueous fluid, where the composition comprises at least one transition metal ion source.
An aqueous fluid comprising:
- water;
- at least one viscoelastic surfactant (VES) in an amount effective to increase the viscosity of the aqueous fluid, where the VES is selected from the group consisting of amines, amine salts, quaternary ammonium compounds, amine oxides, ethoxylated fatty amines, methyl ester sulfonates, betaines, modified betaines, sulfosuccinates, and mixtures thereof;
- and
- a composition in an amount effective to reduce the viscosity of the gelled aqueous fluid, where the composition comprises:
- from about 0.01 to about 300 ppm, based on the total fluid of at least one transition metal ion source;
- at least one chelating agent;
- and
- at least one reducing agent source;
- where the composition reduces the viscosity of the gelled aqueous fluid by a mechanism selected from the group consisting of disaggregating a micelle structure of the VES, rearranging a micelle structure of the VES, chemically altering an effective amount of the VES, and combinations thereof.
Dependencies are inferred from the claim text.