Abstract: The composition and method for treating carbonate reservoirs provides a treatment fluid for the acid treatment of stratified subterranean formations. The treatment fluid is injected into a non-problematic or high permeability zone of a carbonate reservoir. The treatment fluid is formed from a zwitterionic viscoelastic surfactant, which forms about 7.5 vol % of the treatment fluid, hydrochloric acid forming about 15.0 vol % of the treatment fluid, and a corrosion inhibitor forming about 0.6 vol % of the treatment fluid, the balance being brine. The treatment fluid gels as the hydrochloric acid reacts with carbonate of the carbonate reservoir, thus forming a diverting block in the non-problematic or high permeability zone. Following formation of the diverting block, a further volume of the treatment fluid is injected into the carbonate reservoir. The diverting block diverts the treatment fluid into a problematic or low permeability zone of the carbonate reservoir.