Method of treating formation to remove ammonium ions without decreasing permeability

Abstract From the Canadian patent

Abstract of the Disclosure, A method of treating a subterranean formation which has undergone an in situ leaching operation which utilized an ammonium carbonate and/or bicarbonate lixiviant. In such a leach operation, ammonium ions will absorb into the clay in the formation and will present a threat of contamination to any ground waters that may be present in the formation. The present method involves flushing the formation with a strong alkaline solution, e.g. sodium or calcium hydroxide to, convert the ammonium ions to ammonia which is easily carried from the formation by the alkaline solution. The alkaline solution is modified by adding a monovalent metal salt e.g. sodium chloride, which …