Abstract: An aqueous caustic solution and an aqueous solution containing a polyvalent cation dissolved therein are sequentially injected into the near well bore environment of a subterranean sandstone formation interposed by an aqueous spacer. The aqueous caustic solution is caused to reside within the near well bore environment for a period of time sufficient to allow the caustic to interact with the sandstone formation so as to cause a portion of the caustic injected to be held within the near well bore environment. The subsequently injected polyvalent cation and the portion of caustic react within the near well bore environment and form an insoluble precipitate which preferentially reduces the permeability of the relatively highly permeable zones in the near well bore environment thereby improving vertical conformance and flow profiles of fluids subsequently injected into or produced from the formation.