A method is described for treating a subterranean formation with a low viscosity fluid system that contains a viscoelastic surfactant at a concentration too low to viscosify the fluid, but that is concentrated in the formation so that the fluid system gels. The fluid optionally contains a formation-dissolving...http://www.google.de/patents/US7770644?utm_source=gb-gplus-sharePatent US7770644 - Self diverting matrix acid
