METHODS AND SYSTEMS FOR ACIDIZING SUBTERRANEAN FORMATIONS WITH TREATMENT FLUIDS CONTAINING DUAL-FUNCTIONING CHELATING AGENTS

摘要

When used outside the pH range at which metal ion complexation normally occurs, aminopolycarboxylic acids can moderate the reaction rate of acids with carbonate minerals. Methods for treating a subterranean formation can comprise: providing a treatment fluid comprising an aqueous carrier fluid, an acid, and a chelating agent comprising an aminopolycarboxylic acid, the treatment fluid having a pH below that at which the carboxylic acid groups of the chelating agent are substantially protonated and the chelating agent is ineffective for complexing a metal ion; introducing the treatment fluid into a subterranean formation comprising a carbonate mineral; reacting the acid with the carbonate mineral, such that the acid at least partially spends and the pH of the treatment fluid rises; and once the pH of the treatment fluid rises above a pKa value for one or more of the carboxylic acid groups, complexing a metal ion with the chelating agent.