Methods are provided for removing filter cake containing a bridging agent soluble in a carboxylic acid salt from a formation fluids producing zone penetrated by a well bore. The methods basically comprise the steps of introducing in an aqueous carrier liquid a carboxylic acid ester and a base for slowly catalyzing the hydrolysis of the ester and forming a carboxylic acid salt therewith into the producing zone, and allowing the base to catalyze the hydrolysis of the carboxylic acid ester to form the carboxylic acid salt so that the carboxylic acid salt dissolves the bridging agent and the filter cake is removed.