Determination of equivalent alkane carbon number for West Siberian oils as a stage of optimisation in surfactant-polymer compositions for chemical flooding

The hydrophobicity of oil and oil products can be characterised in terms of its equivalent alkane carbon number (EACN). This characteristic can be determined on the basis of the correlation between the interfacial tension data and other characteristics for homologous oils and a number of alkanes having subsequent interpretation for oil and oil products. The EACN is a useful metric for selecting an effective surfactant for the emulsification of oil and oil products. The research is aimed at determining the equivalent alkane car-bon number of various crude oil samples obtained in the oil fields of Western Siberia using standard high-performance compositions of imported and domestic industrial sulphonate surfactants. In order to determine the EACN of oil and oil products, the S* characteristic was applied representing the optimal NaCl concentration (optimum salinity) in the aqueous surfactant phase, as well as providing the minimum surface tension and formation of the maximum microemulsion volume during the phase experiment at the interface with the hydro-carbon phase. Direct determination of the interfacial tension at the "oil / surfactant solution" interface was car-ried out with a tensiometer using the spinning drop method at a temperature of 87 °С. Linear dependencies are identified in accordance to the empirical correlation equations between the EACN, surfactant parameters and phase behaviour parameters of aqueous surfactant solutions and oil or a mixture of hydrocarbons. The K characteristic parameter of the proposed three standard surfactant compositions is determined to be consistent with the literature data for individual surfactants. The composition of industrial surfactants for determining the EACN of oil and oil products is proposed. The equations of linear regression for the logS* ~ EACN dependency with high correlation coefficients (R² = 0.9444-0.9999) are obtained, resulting in the determination of the EACN for kerosene and seven oil samples from Western Siberian oil fields. Promising surfactants can be selected on the basis of this indicator for reducing interfacial tension in the "hydrocarbon / water solution" system, as well as for predicting the most effective composition for obtaining emulsions.

oil, hydrocarbon, surfactant, equivalent alkane carbon number, interfacial tension, microemulsion