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.