Abstract: A method for strengthening a subterranean formation by injecting an aqueous gellable composition containing a cross-linkable polymer into the subterranean formation through a wellbore to increase the strength of the subterranean formation while retaining the ability of the subterranean formation to produce fluids.

Abstract: A composition containing a chelating agent and an amino carboxylic acid and a method for breaking a gel formed by a crosslinkable polymer and a crosslinking agent. The composition may also be used for selectively removing crosslinked polymer gels from an oil-bearing zone in a subterranean formation in the presence of a water formation plugged by a crosslinkable polymer and a crosslinking agent. Aqueous solutions of phosphonates and sulfonates are also useful in the method.

Abstract: An aqueous polymer composition containing water and hydrophilic polymers and a method for treating subterranean formations with the composition to reduce formation permeability. The hydrophilic polymers are a mixture of high-molecular-weight polymers having a molecular weight of at least about 2,000,000, and low-molecular-weight polymers having a molecular weight of up to about 1,000,000.

Abstract: A method for strengthening a subterranean formation by injecting an aqueous gellable composition containing a cross-inkable polymer into the subterranean formation through a wellbore to increase the strength of the subterranean formation while retaining the ability of the subterranean formation to produce fluids.

Abstract: A gel-breaking/gel-inhibiting composition containing at least one carboxylic acid or salt thereof is dispersed in a hydrophobic carrier fluid to break down a cross-linked polymer gel or inhibit the gelation of a polymer gel used in plugging in permeable subterranean formations containing oil-bearing zones and water-bearing zones. The composition may be used to selectively restore permeability to oil-bearing zones in formations containing a cross-linked polymer gel or to inhibit gelation in an oil-bearing zone by injection into the oil-bearing zone prior to or after treatment of the formation containing the oil-bearing zone with an aqueous polymer solution.

Abstract: Hydrocarbon bearing earth formations are treated to reduce formation permeability and fill void spaces by injecting a polymer gel solution having an artificial matrix material dispersed therein and comprising beads of materials such as polystyrene and polycarbonate having densities substantially the same as the density of the polymer gel to improve distribution of the artificial matrix material into such void spaces.