Nanofluids of Kaolinite and Silica in Low Saline Seawater (LowSal) with and without Surfactant: Interfacial Tension and Wettability Alteration of Oil-Water-Rock System for Low Salinity-Enhanced Oil Recovery

Low salinity water injection (LSWI) has gained popularity recently as a potential enhanced oil recovery (EOR) method. The efficiency of LSWI can be improved with the advent of nanotechnology. Nanofluids can alter the wettability of the solid surface from intermediate-wet to water-wet, a condition most favorable to enhance the oil displacement efficiency. Studies have been reported in the literature on the use of nanoparticles and surfactants with LSWI mainly for carbonate rock and synthesized saline water containing mainly sodium salt; however, not much information is available for sandstone rock and the use of low saline seawater (LowSal). Also, a comparative study on the use of silica and kaolinite nanofluids in LowSal has not yet been explored in detail to understand their impact on the wettability alteration and interfacial tension (IFT) of the oil-nanofluid-rock system. Thus, in this work, silica and kaolinite nanofluids have been prepared in LowSal with varying concentrations (0-2000 ppm) without and with an anionic surfactant, dioctyl sodium sulfosuccinate (AOT), to assess their impact on the IFT and wettability alternation (through contact angle measurements) of the oil-nanofluid-rock system. Three different oil samples, viz., model oil A, model oil B, and light crude oil to represent acidic, basic, and weakly basic oil systems, respectively, have been considered. An intermediate-wet quartz plate is used to mimic the properties of the sandstone rock. A detailed mechanism has been highlighted to ascertain the impact of nanofluids on the IFT and wettability alteration of the representative rock sample from an intermediate-wet to water-wet condition based on the Gibbs adsorption isotherm, scanning electron microscopy (SEM), and energy-dispersive X-ray (EDXA/EDS/EDX) studies. The results are outlined to understand the possible future applications of silica and kaolinite nanofluids for enhanced oil recovery processes.