A method of treating a subterranean formation with a retarded self-diverting fluid system. The method includes contacting the formation with a mixture of acid, chelating agent, and betaine surfactant in which the betaine surfactant is mixed with an aqueous solution of the chelating agent in which the pH has been adjusted to a pH of below about 3.0, but above the pH at which the free acid of the chelating agent precipitates, and the resulting fluid system is utilized for both acid fracturing and matrix stimulation, as well as workover procedures such as scale and filter cake removal, especially in high temperature formations.