Abstract: A water-producing zone in a reservoir penetrated by a gravel-packed well is isolated by placing a bridge plug in the well tubing adjacent to the top of the water-producing zone, then placing a first coarse sand on the bridge plug, followed by a fine sand on top of the coarse sand, and finally by placing a flowable resin on top of the fine sand where it spreads out through the gravel pack to provide a flow barrier to water.

Abstract: A mixture of an epoxy material and two hardeners is placed in a subsurface zone in which it is desired to form an impermeable zone, and the epoxy is thereafter allowed to harden. The epoxy material and hardeners are characterized inthat: (1) each hardener has a different activation temperature; (2) the amount of each hardener in the mixture is less than that required to totally react the epoxy material; (3) the epoxy material has a low viscosity at subsurface conditions of temperature and pressure; (4) the epoxy material is substantially immiscible with any fluids which are present in the subsurface area; and (5) the hardening time of the epoxy material is of short duration at subsurface conditions of temperature and pressure.

Abstract: A high pH solution containing a silica material and an inorganic fluoride salt which hydrolyzes to form hydrofluoric acid are introduced into a subterranean zone where the pH is reduced by the acid whereby the silica material forms a gel and plugs the subterranean zone. The pH at which gelling occurs can be increased by adding a soluble inorganic salt to the solution.