The oil/water interfacial tension (IFT) is a key index of the properties of chemical enhanced oil recovery (EOR) displacement systems with surfactant. The studies showed that different oil and water often required different surfactant formulations to reduce IFT. The crude oil compositions in different oilfields differ with each other. Therefore, it requires different surfactant formulations to fit oil properties. It is necessary to reveal what kinds of components in crude oil have crucial influence on IFT reducing ability of surfactants, so as to optimize surfactant formulations for certain crude oil being performed efficiently.

Daqing Oilfield crude oil was cut into five oil fractions with different boiling range by true boiling point distillation method. Group compositions (saturates, aromatics, resins, wax and asphaltene) of high boiling fraction and vacuum residuum were further separated by column chromatography and solvent extraction method. Five oil fractions and seven group compositions of crude oil were obtained. The effects of these fractions and chemical compositions on the performances of surfactants in reducing IFT were investigated.

The IFT for the crude oil fractions and group components separated were tested using sodium alkylbenzene sulfonate (ABS) surfactants with different structures. The results indicated that oil fractions and group components have different impact on surfactants in reducing IFT. Low IFT value could be obtained for 200–350 °C and 350–400 °C oil fractions by ABS with carbon chain length of C16-C18 or C16 alkyl methyl benzene sulfonate. The unfavorable interfacial activity for oil fractions were low and high boiling point fractions. The effect degree order of IFT reducing ability for group components by ABS surfactants was: resins > aromatics > saturates > wax. High boiling point fractions and heavy components of resins and aromatics significantly influence on the performance of ABS surfactants in reducing IFT. Based on these results, an industrial product HABS was developed which could reach ultralow IFT between crude oil and surfactant solutions.

Understanding the effect of crude oil components on the performances of surfactants in reducing oil/water IFT will help us to screen and optimize surfactant oil displacement formulations targeted according to the different properties of crude oils.

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