Treatment of water thickened systems

Claim 1

In the process to effect enhanced recovery of oil from a subterranean reservoir with an aqueous driving medium whose viscosity has been increased by providing a water-soluble polysaccharide polymeric mobility control agent to the medium, the improvement which comprises providing an amine in the medium in the reservoir in an amount of between about 0.0001 to about 1.0 weight percent of the medium, which amine is one of an alkylene polyamine, an alkanol amine, an alicyclic polyamine, or a mixture of two or more of them, the aforesaid amines being selected such that when added at 300 ppm concentration in a hydroxyethylcellulose medium having a 90 cps viscosity and the medium temperature is maintained at 35° C. a medium is achieved which retains at least 60% of its measured viscosity after 24 hours and thereafter there is less than 30% additional measured viscosity loss at the end of 10 days, the O 2 concentration of the medium being reduced to approximately 1 ppm by nitrogen purging prior to addition of the hydroxyethylcellulose polymer, and sodium sulfite or sodium dithionite at 25 ppm and 5 ppm concentration, respectively, is post-added to the medium at ambient temperature after addition of said hydroxyethylcellulose polymer and said amines.