Abstract: A method for removing or dissolving calcareous materials in a subterranean formation or in a wellbore consists of two basic steps. In the first step, an aqueous acid solution is injected into the formation or wellbore. The aqueous acid solution contains between from about 15 to about 99 weight percent of an organic acid selected from formic acid, acetic acid or a mixture of formic acid and acetic acid. Water or brine is then injected into the formation or wellbore. The amount of water or brine injected into the formation or wellbore is an amount sufficient to reduce the concentration of organic acid in the formation or wellbore to no greater than 10 weight percent.