| abstract |
Fluids viscosified with viscoelastic surfactants (VESs) may have their viscosities reduced (gels broken) by the direct or indirect action of a breaker composition that contains at least one mineral oil, at least one polyalphaolefin oil, and/or at least one saturated fatty acid. The breaker may initially be dispersed oil droplets in an internal, discontinuous phase of the fluid. In one non-limiting embodiment, the breaker, e.g. mineral oil is added to the fluid after it has been substantially gelled. The breaking composition is believed to act possibly by rearranging, disaggregating or otherwise attacking the micellar structure of the VES-gelled fluid in a non-spontaneous, rate controlled manner at elevated fluid temperatures. In a specific, non-limiting instance, a brine fluid gelled with an amine oxide surfactant can have its viscosity broken with a light, low viscosity paraffinic mineral oil. |