US Patent 7858563 Wellbore treatment with hydrocarbon-responsive fluid containing oligomeric viscoelastic surfactant

A treatment of a subterranean formation which contains a hydrocarbon-bearing zone, is carried out using a hydrocarbon-responsive fluid thickened with an oligomeric surfactant consisting of from 2 to 8_linked surfactant monomer subunits. The process of treatment comprises(i) mixing a thickening amount of oligomeric surfactant with an aqueous liquid to make a viscoelastic treatment fluid,(ii) pumping said viscoelastic treatment fluid through a wellbore and into the subterranean formation, where (iii) contact with hydrocarbons within the formation dissipates the viscosity of the treatment fluid.