Methods and compositions are disclosed for controlled addition of components
that decrease the viscosity of the viscoelastic surfactant fluids or for controlled
changes in the electrolyte concentration or composition of the viscoelastic surfactant
fluids. One aspect of the invention relates to the use of internal breakers with
a delayed activation. Another aspect of the invention relates to the use of precursors
that release a breaking system such as alcohol by a process such as melting, slow
dissolution, reaction with a compound present in the fluid or added to the fluid
during or after the step of injecting, rupture of an encapsulating coating and
de-adsorption of a breaking agent absorbed into solid particles. In another aspect
of the invention, alcohols are included in a pad to reduce the low-shear viscosity
and reduce the resistance to flow of the treatment fluids during a desired phase
of the treatment.
