Process for recovering oil from an underground deposit

摘要

In a process for recovering largely emulsion-free oil from an underground deposit of medium or high salinity by injecting 1 to 20% solution or dispersion in formation water of carboxymethylated oxethylates of the formula R-(OCH2CH2)n-OCH2-COOM, in which R is a linear or branched aliphatic radical having 4 to 20 carbon atoms or an alkyl- or dialkyl-aromatic radical having 1 to 14 carbon atoms in the alkyl group, n is 3 to 30 and M is an alkali metal ion, alkaline earth metal ion or ammonium and the degree of carboxymethylation is between 10 and 90%, into an injection well, the surfactant is selected such that the phase inversion temperature of the crude oil/formation water/surfactant/optional additives system is 0 to 10 DEG C above the temperature of the deposit.