Process for improving conformance and flow profiles in a subterranean sandstone formation

A process for improving vertical conformance and flow profiles of fluids injected into or produced from a subterranean sandstone formation having a zone of relatively high permeability and a vertically juxtaposed zone of relatively low permeability, the sandstone formation being penetrated by a well bore in fluid communication therewith and having a near well bore environment which exhibits relatively homogeneous horizontal properties, the process comprising:

• injecting via said well bore into said zone of relatively high permeability in said near well bore environment a caustic aqueous solution having caustic dissolved therein;
• shutting in said well bore for a period of time sufficient to allow said caustic to interact with said sandstone formation thereby resulting in at least a portion of said caustic being held within said near well bore environment;
• injecting via said well bore into said zone of relatively high permeability in said near well bore environment an aqueous spacer slug;
• and, thereafter
• injecting via said well bore into said zone of relatively high permeability in said near well bore environment a polyvalent cation containing solution having a polyvalent cation dissolved therein that is reactive with said caustic, permitting said polyvalent cation solution to react with said at least a portion of said caustic to form an insoluble precipitate within said zone of relatively high permeability in said near well bore environment, said insoluble precipitate reducing the permeability of said zone of relatively high permeability in said near well bore environment and reducing the ratio of the permeability of said zone of relatively high permeability to the permeability of said zone of relatively low permeability.