Physicochemical properties of ethoxylated sulfosuccinate surfactants and their interfacial properties when mixed with a betaine surfactant
To enhance oil recovery in low-permeability reservoirs through the injection of low-mineralized water,the foaming behavior,surface tension and interfacial tension of a series of ethoxylated sulfosuccinate surfactants(C12EO6-CnMS,n=10,12,14 and 16)were investigated.The interfacial properties of mixtures of C12EO6-CnMS and a betaine surfactant were also studied,and the minimum alkane carbon number(Nmin)of the mixed system was obtained.The experimental results showed that C12EO6-CnMS exhibited low-foaming properties.The critical micelle concentration(cmc)of the surfactants decreased when the carbon chain length of the fatty alcohol(n)attached to ester group was increased.The addition of inorganic salts could reduce the cmc of C12EO6-CnMS,and the more inorganic salt,the more reduction of cmc.The mixed system of C12EO6-C10MS(in which the fatty alcohol carbon chain length was C10)and the betaine surfactant C16ZC displayed synergistic effect,exhibiting smaller cmc.The interfacial tension(IFT)between C12EO6-CnMS and n-alkanes increased as the carbon chain length(n)of the surfactants increased.The scanning of IFT values between C12EO6-CnMS and a series of n-alkanes was operated to determine the minimum alkane carbon number(Nmin)for the surfactant.Notably,the Nmin value increased with the addition of inorganic salts.In the presence of 0.5%-1%NaCl,the Nmin values for C12EO6-C10MS and C12EO6-C12MS are 12-14.As for surfactant mixtures,in the presence of 0.5%-1%NaCl,when the molar ratios of C12EO6-C10MS to C16ZC are 4/1,3/2 and 2/3,the mixtures exhibited synergistic effect in reducing interfacial tension,achieving ultra-low to low IFT values(10-3-10-2 mN/m)against dodecane,tetradecane and cetane.It makes the system suitable for enhanced oil recovery(EOR)of crude oil with equivalent alkane carbon number(EACN)of 12-16.
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