Spontaneous in-situ emulsification and enhanced oil recovery using functionalised silica nanoparticles: Insights from spontaneous imbibition and micromodel flooding tests

This study investigates the potential of functionalised silica nanoparticles (SiO₂ NPs) for enhanced oil recovery (EOR), employing environmentally friendly and cost-effective materials. SiO₂ NPs were optimally modified with ammonium lauryl sulfate (ALS) and sodium (C14-16) olefin sulfonate (SOS) surfactants under optimal conditions without binding agents, representing their first application in EOR. Characterisation techniques, including Fourier-transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA), confirmed the effective functionalisation of SiO₂ NPs. Transmission electron microscopy (TEM) images revealed that the morphology, structure, and shape of the NPs remained unchanged post-functionalisation, with an average diameter of 20 nm. The performance of ALS-NPs and SOS-NPs was assessed through spontaneous imbibition and microfluidic tests. ALS-NPs and SOS-NPs achieved oil recovery rates of approximately 66 % and 70 %, respectively, in spontaneous imbibition tests. Microfluidic model tests corroborated these findings, with oil recovery rates of approximately 74 % for ALS-NPs and 80 % for SOS-NPs. Both functionalised nanofluids demonstrated superior oil recovery compared to surfactants alone and non-functionalised SiO₂ NPs. The application of these nanofluids facilitated the spontaneous formation of smaller, more stable emulsion droplets, enhancing displacement efficiency and reducing pore blockages. Moreover, the nanofluids improved oil recovery by reducing interfacial tension (IFT), altering rock wettability, and forming stable oil-in-water emulsions. The grafting approach of ALS- and SOS-based nanofluids demonstrates greater efficiency by requiring lower surfactant concentrations, thereby making the process cost-effective.