Preparation of polyoxypropylene surfactant-based nanoemulsions using phase inversion composition method and their application in oil recovery

• Polyoxypropylene surfactant was used to prepare nanoemulsions using the phase inversion composition (PIC) method. • Polyoxypropylene surfactant are more effective than conventional surfactant in nanoemulsion formation by the PIC method. • The obtained nanoemulsions will be an important candidate for the application in enhanced oil recovery. Emulsification using phase inversion composition (PIC) was achieved by changing the composition of surfactants at a constant temperature. The method has great potential to scale up applications due to the ease in the formation of nanoemulsions and the relatively low energy involved. Surfactants containing composition-sensitive polyoxyethylene (POE) chains are widely used to prepare nanoemulsions using the PIC method. It is, therefore, anticipated that surfactants containing composition-sensitive polyoxypropylene (POP) chains can also be used to prepare nanoemulsions using the PIC method. The POP surfactant D230-2OA, containing short POP chains, was obtained from the electrostatic interactions between hydrophilic POP diamine (D230) and hydrophobic oleic acid (OA). The synthesized D230-2OA was used as an emulsifier in the preparation of the n -dodecane-in-water nanoemulsion using the PIC method. The effects of D230-2OA concentration, oil-to-surfactant weight ratio, and NaCl concentration on the droplet size of the nanoemulsions was investigated using dynamic light scattering (DLS). The morphology of the nanoemulsion was characterized using cryogenic transmission electron microscopy (cryo-TEM). The wettability of the crude oil–saturated quartz plate before and after treatment with nanoemulsions was obtained using contact angle measurement. A core flooding experiment demonstrated the efficiency of the diluted nanoemulsion in enhanced oil recovery, with an additional recovery of 21.30%. The nanoemulsion prepared with the POP surfactant as the emulsifier using the PIC method has wide application in petroleum recovery.