Abstract: The water permeability and the production of salt water from a subterranean oil bearing formation is reduced by introducing a viscous aqueous polymer composition into the formation which will subsequently form a crosslinked gel therein, and thereafter introducing a hydrocarbon cement slurry into the formation.

Abstract: A method of controlling the permeability of underground well formations by the placement of a chemical barrier is provided. A first fluid and a second fluid are substantially simultaneously injected into the formation via a well bore wherein the first fluid generally contains either a viscosifying agent or a permeability reducing agent and the second fluid contains a sealant. As the two fluids extend radially from the well bore, the injection pressures of the first and second fluids are substantially balanced such that migration of the second fluid into portion of the formation occupied by the first fluid is inhibited.