Recovery of petroleum with chemically treated high molecular weight polymers

Claim 1

In a process of flooding an oil-bearing subterranean formation in communication with injection means and production means, wherein an aqueous, high molecular weight polymer solution is injected into the formation to displace oil toward the producing means, the improvement comprising: (a) reacting in an aqueous solution a polymer-oxidizing oxidant selected from the group consisting of peroxides and compounds of the formula MOX wherein M is an alkali metal or ammonium and X is a halogen with a polymer of average molecular weight sufficiently high to cause substantial plugging of the reservoir on injection in aqueous solution to reduce the polymer to an average molecular weight which does not cause substantial plugging during injection into the reservoir, (b) thereafter reacting a reducing agent with the polymer of reduced average molecular weight to terminate degradation by the oxidant at a predetermined average molecular weight, (c) injecting an aqueous solution of the degraded polymer into the reservoir through the injection means, and (d) displacing said aqueous degraded polymer solution a substantial distance into or through said formation.