Characteristic Curvature Assessment of Some Natural Surfactants for Chemical Enhanced Oil Recovery Applications in Nigeria

Abstract Chemical enhanced oil recovery (CEOR) application of natural surfactants is based on potential interfacial tension (IFT) alterability and eco-friendly considerations. The reduced IFT is associated with microemulsion formation in relation to a surfactant’s characteristic curvature. Lately, surface activities of natural surfactants have gained interest in Nigerian laboratory studies with no attention given to their hydrophilicity/hydrophobicity. This research focuses on molecular weight determination, micelle formation, and characteristic curvature evaluation of readily available natural surfactants. Four plants that are known to possess relevant surfactant properties were selected for this evaluation. Freezing point dipping method was used to determine the average molecular weight of each surfactant. Critical micelle concentration (CMC) was ascertained by electric conductivity tests. Characteristic curvature was evaluated from microemulsion formulations of toluene and aqueous surfactant mixtures. Formulated aqueous surfactant mixture consists of a combination of selected natural surfactant and a reference surfactant. Sodium dodecylsulphate (SDS) was adopted as the reference surfactant throughout this work. The analysis was configured in line with the hydrophilic-lipophilic deviation (HLD) model set to 0. Results yielded average molecular weights of examined surfactants between 128.3 g/mol to 186.7 g/mol. Critical micelle concentrations values of 0.45 to 0.60 were derived for all natural surfactants. Estimated characteristic curvature values suggested hydrophobicity with values from 0.116 to 0.194. As a consequence, these natural surfactants possess a tendency to form reverse micelles due oleic phase attraction. Their low positive values make them suitable for lowering IFT in order to mobilise trapped formation oil.