Patent ID: 7084094

Claim:
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, which process comprises: a) sequentially injecting into the formation: (i) optionally an aqueous pre-flush fluid, the pre-flush fluid not comprising a crosslinking agent; (ii) before any crosslinking agent is injected, 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 groups, phosphonate groups, or combination of carboxylate and phosphonate groups and a number average molecular weight in the range of 250,000 to 12,000,000; (iii) optionally an aqueous spacer fluid; (iv) an aqueous solution of a crosslinking agent. which crosslinking agent comprises a complexed zirconium compound, a complexed titanium compound or a mixture thereof; and (v) optionally an overfiush fluid; 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.