Patent ID: 7287588

Claim:
A method for selectively blocking water inflow from a water-producing formation of a hydrocarbon well, the method comprising: injecting into the well a controlled-gelation aqueous solution containing (a) a hydrophobically-aggregating gelling agent, said gelling agent being a water-soluble copolymer comprising hydrophilic and hydrophobic monomer units, and (b) an effective amount of an inhibitor which suppresses hydrophobic aggregation of the gelling agent and which is soluble in water but substantially insoluble in hydrocarbons, whereby when the controlled-gelation aqueous solution contacts a hydrocarbon producing formation the inhibitor continues to suppress said hydrophobic aggregation so that gelation is suppressed, and when the controlled-gelation aqueous solution contacts a water producing formation the inhibitor disperses so that gelation occurs and the formation is blocked.