FIELD: oil and gas industry.
SUBSTANCE: group of inventions relates to surfactant compositions containing anionic surfactants along with nonionic surfactants, and to the use of such compositions in methods of chemical enhanced oil recovery. Surfactant composition for use in chemical enhanced oil recovery. Surfactant composition contains at least: i) an anionic salt of an alkyl alkoxylated sulphate and ii) a non-ionic alcohol ethoxylate, where the weight ratio of i)/ii) ranges from 6:1 to 1:6. Also disclosed is the use of a surfactant composition in chemical enhanced oil recovery, where said surfactant composition is a surfactant composition and a method for chemical enhanced oil recovery of a subterranean formation drilled by at least one injection well and one production well. Method includes i) pumping a surfactant composition into an injection well, whereby said surfactant composition is in contact with crude oil present in said subterranean formation, to reduce interfacial tension of said crude oil to ultra-low values at level of 10−2 mN/m or lower and ii) extraction of crude oil from underground formation from production well. Said surfactant composition is capable of reducing interfacial tension values at temperatures from 25 °C to 70 °C and in saturated salt solutions, having from 4% to 15% of the total content of dissolved solids, at least part of said dissolved solids is divalent cations.
EFFECT: compositions provide ultra-low values of IFT at 10−2 mN/m and less for a number of heavy and light crude oils with different properties (SARA composition and densities).
15 cl, 9 dwg, 7 tbl, 3 ex
