The injectability of injection wells can be increased in oil extraction by means of water flooding, by injecting a solution, dispersion, or emulsion of carboxymethylated oxethylates of the formula R-O(C3H6O)m(C2H4O)nCH2COOM in formation water or flooding water and, optionally, crude oil, into the injection well, the tenside being selected so that the phase inversion temperature of the system of reservoir oil/formation water or flooding water/tenside/optional additives lies at least 12 DEG C. above the reservoir temperature.
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