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 gelable composition containing an organic, water soluble polymer cross-linkable with a multivalent cation and a retarded cross-linking system consisting essentially of chromium trichloride and monosodium glutamate and a method for reducing the permeability of the subterranean formation using the composition.

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 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: Hydraulic fractures which extend between a hydrocarbon fluid producing zone of an earth formation and a water-producing zone are sealed with respect to the water-producing zone by simultaneously injecting a non-sealing fluid such as crude oil, diesel fuel or brine into the portion of the fracture extending within the hydrocarbon producing zone and injecting a settable gel composition such as a polyacrylamide polymer cross-linked with inorganic transition metals into the portion of the fracture extending within the water-producing zone. The flow rates of the simultaneously pumped fluids are controlled in accordance with the ratio of the respective fracture heights and the viscosity and density of the respective sealing and non-sealing fluids. One fluid is typically pumped through the well annulus while the other fluid is pumped through a tubing string which is sealed from the annulus by a conventional packer disposed at the interface between the hydrocarbon and water-bearing zones.

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.