Abstract: A new and improved composition and method for profile modification of subterranean formations characterized by high reservoir temperatures and/or harsh brine conditions are disclosed. The new and improved profile modification agents comprise a gelable composition comprising:(a) water;(b) a water-thickening and crosslinkable amount of a water-dispersible copolymer comprising from about 30 to about 99 mol % of units derived from at least one N-sulfohydrocarbon substituted acrylamide monomer copolymerized with from about 1 to about 70 mol % of units derived from at least one other monomer bearing a carboxyl group or a carboxyl precursor group; and(c) an amount of a polyvalent metal sufficient to crosslink the copolymer to form a stable gel. The profile modification agents are effective to alter the permeability of preselected portions of an underground formation by forming strong gels which are stable in harsh brine at temperatures of up to about 120.degree. C.

Abstract: A new and improved composition and method for profile modification of subterranean formations characterized by high reservoir temperatures and/or harsh brine conditions are disclosed. The new and improved profile modification agents comprise a gelable composition comprising:(a) water;(b) a water-thickening and crosslinkable amount of a water-dispersible copolymer comprising from about 30 to about 99 mol % of units derived from at least one N-sulfohydrocarbon substituted acrylamide monomer copolymerized with from about 1 to about 70 mol % of units derived from at least one other monomer bearing a carboxyl group or a carboxyl precursor group; and(c) an amount of a polyvalent metal sufficient to crosslink the polymer to form a stable gel. The profile modification agents are effective to alter the permeability of preselected portions of an underground formation by forming strong gels which are stable in harsh brine at temperatures of up to about 120.degree. C.

Abstract: Copolymers of 2-acrylamido-2-methylpropane sulfonic acid or its salts are used to maintain the viscosity of aqueous solutions thereof in the presence of divalent salt containing-waters during the enhanced recovery of petroleum from sub-terranean petroleum-bearing deposits.

Abstract: Water-soluble cross-linked cationic polysulfonium derivatives of poly(thiodiethanol)ethers are useful flocculants for suspended solids in aqueous medium.

Abstract: Water-soluble cross-linked polysulfonium derivatives of poly(thiodiethanol) ethers are provided by reacting the ethers with difunctional sulfide-reactive alkylating agents.