Abstract: A process for treating a hydrocarbon-bearing formation having at least one hydrocarbon bearing zone and at least one water bearing zone wherein the ratio of the permeability of the hydrocarbon bearing zone(s) to the permeability of the water bearing zone(s) is in the range of from 1:20 to 3:1 comprising: a) sequentially injecting into the formation: (i) an aqueous polymer solution comprising 0.01 to 0.5 weight percent of a water-soluble polymer having from 0.01 to 7.5 mole % of crosslinkable carboxylate and/or phosphonate groups and a molecular weight in the range of 250,000 to 12,000,000; and (ii) an aqueous solution of a crosslinking agent; and b) back-producing the aqueous polymer solution over the crosslinking agent so that the polymer crosslinks within the formation to form a gel which is collapsible to allow hydrocarbon flow.

Abstract: A process for treating a hydrocarbon-bearing formation having at least one hydrocarbon bearing zone and at least one water bearing zone wherein the ratio of the permeability of the hydrocarbon bearing zone(s) to the permeability of the water bearing zone(s) is in the range of from 1:20 to 3:1 comprising: a) sequentially injecting into the formation: (i) an aqueous polymer solution comprising 0.01 to 0.5 weight percent of a water-soluble polymer having from 0.01 to 7.5 mole % of crosslinkable carboxylate and/or phosphonate groups and a molecular weight in the range of 250,000 to 12,000,000; and (ii) an aqueous solution of a crosslinking agent; and b) back-producing the aqueous polymer solution over the crosslinking agent so that the polymer crosslinks within the formation to form a gel which is collapsible to allow hydrocarbon flow.

Abstract: A method of recovering or increasing the recovery of oil and/or gas from an underground formation involving injecting into the formation, preferably in the form of an aqueous solution, at least one mono alkyl ether of polyethylene glycol in which the alkyl group has 3-5 carbons and the polyethylene glycol contains 3-6 ethylene oxy units e.g. butyl ether of triethylene glycol. Especially preferred are mixtures comprising that and at least one mono alkyl ether of mono or di ethylene glycol e.g. a mixture of butyl triglycol ether, butyl tetraglycol ether, butyl pentaglycol ether and butyl diglycol ether. The method of the invention may be applied to well stimulation treatments such as water blocking, sand consolidation, sandstone acidizing and methods of increasing the recovery of oil such as tertiary oil recovery.