The influence of temperature, pressure, salinity, and surfactant concentration on the interfacial tension of the N-octane-water system

An elaborate experimental study was conducted for the determination of the interfacial tension ( IFT) values for a n-octane/water system for a wide range of experimental conditions of temperatures, pressures, and salt concentrations that exist in a natural oil reservoir. Three different surfactants were used in the analysis: dodecyl benzene sulfonic acid sodium salt, sodium dioctyl sulfosuccinate, and hexadecyl trimethyl ammonium bromide. The measured IFT values were correlated linearly to pressure ( P), temperature ( T), and salt concentration ( CB) in the aqueous phase. There was an almost 20-fold reduction noticed in the IFT values with the addition of surfactants. This behavior was best related by an exponential expression in terms of the surfactant concentration ( CS) as given below: IFT = Exp (a(0)/a(1) + C-S(a2)) + a(3)T + a(4)P + a(5)C(B) The experimental data for the three surfactants can be represented independently by the above correlation. The absolute average percentage error was always less than 7% for the different data sets considered.