A method is given for treating a subterranean formation penetrated by a wellbore with a viscosified fluid. The fluid contains a solid hydrolysable polyacid that upon dissolution and hydrolysis releases an acid that is a breaker for the viscosifying system. Suitable solid hydrolysable polyacids include...http://www.google.de/patents/US20050252659?utm_source=gb-gplus-sharePatent US20050252659 - Degradable additive for viscoelastic surfactant based fluid systems
