Micellar solubilization of petroleum fractions by heavy alkylbenzene sulfonate surfactant

The primary mechanism of surfactant enhanced oil recovery (EOR) has always been ascribed to ultralow interfacial tension (IFT) between oil and dispalcing fluid by forming middle-phase microemulsion. However, it is found in field trials that oil can be largely produced by low concentration surfactant flooding without producing microemulsion. Herein, a widely used EOR surfactant, heavy alkylbenzene sulfonate (HABS) was selected to investigate its micellar solubilization behavior for petroleum fractions, alkanes and aromatics, by using UV–Vis spectroscopy, dynamic light scattering, transmission electron microscopy, small-angle neutron scattering (SANS) and fluorescent microscope. Increasing the surfactant concentration resulted in increase of solubilization capacity, and the micellar size increases with the addition of additives, accompanied by an appearance transition from transparent to opaque before and after the maximum solubilization capacity. Alkanes is situated in the micellar core, while aromatics resides in the palisade layer. The evolution from micelle to emulsion has been proved to be a disperse phase mutations once the maximum solubilization capacity is reached. These findings provide support for the contribution of micellar solubilization to surfactant EOR process. [Display omitted] •The mechanism of surfactant EOR at low concentration is clarified.•Micellar solubilization plays a noticeable role in surfactant EOR process.•The solubilization process is revealed by UV–Vis, DLS, TEM and SANS measurements.•1 ton of 0.2 wt% HABS solution can solubilize 650 g alkanes or 200 g aromatics.