Solubility enhancers on basis of allyl alcohol for aqueous surfactant formulations for enhanced oil recovery

A method for the production of crude oil from subterranean, oil-bearing formations comprising at least the following steps:

• (1) Providing an aqueous surfactant composition comprising water and a surfactant mixture,
• (2) injecting said surfactant composition into the subterranean, oil-bearing formation through at least one injection well, thereby reducing the crude oil-water interfacial tension to less than 0.1 mN/m, and
• (3) withdrawing crude oil from the formation through at least one production well,
• wherein the surfactant mixture comprises at least
• (A) a surfactant (A) having the general formula
• R1—O—(CH2CH(R2)O)a—(CH2CH(CH3)O)b—(CH2CH2O)c—R3—Y−M+ (I)
• and
• (B) a solubility enhancer (B) having the general formula
• R4—O—(CH2CH(CH3)O)x—(CH2CH2O)y—R3—Y−M+ (II),
• wherein
• R1 is a hydrocarbon moiety having 8 to 36 carbon atoms,
• R2 is a hydrocarbon moiety having 2 to 16 carbon atoms,
• R3 is selected from the group of
• a single bond,
• an alkylene group —(CH2)o—, wherein o is from 1 to 3,
• a group —CH2—CH(OH)—CH2—,
• R4 is an allyl group H2C═CH—CH2—,
• Y− is an anionic group selected from —COO− or —SO3−,
• M+ is at least a cation selected from the group of alkali metal ions, NH4+,
• and organic ammonium ions,
• a is a number from 0 to 69,
• b is a number from 3 to 70,
• c is a number from 0 to 50,
• x is a number from 1 to 70,
• y is a number from 0 to 50,
• and wherein
• R3, Y−, and M+ in (A) and (B) are identical,
• |x−b|≤10,
• |y−c|≤10, and
• the molar proportion of surfactant (A)/solubility enhancer (B) is from 98:2 to 60:40.