Measurements and Analysis of Disjoining Pressure in Sio2 and Al2o3 Nanoparticles Dispersion

Abstract

Nanoparticles are gaining prominence in enhanced oil recovery (EOR) due to their distinctive capability to alter reservoir wettability and enhance oil displacement. Currently, they are a vital technique for EOR. The stability of the nanoparticles in high salinity plays an essential role in their functionality.  This study has effectively quantified the stability of silica (SiO₂) and alumina (Al₂O₃) nanoparticles in high-salinity reservoirs based on experimental estimations of their disjoining pressure at multiple ionic strengths. The study uses Atomic Force Microscopy (AFM) to measure disjoining pressure. Results show that, SiO₂ nanoparticles exhibit strong Van der Waals attraction at low salinity with weak electrostatic repulsion, leading to a total negative disjoining pressure of about-2.162×10⁻¹² Pa. on the other hand, as salinity increases to 2 M, electrostatic repulsion nearly offsets Van der Waals attraction, indicating an improved stability. In contrast, the Al₂O₃ nanoparticles exhibit strong electrostatic repulsion at low ionic strength concentration, ensuring dispersion. However, as the ionic concentration reaches 2 M, repulsion weakens and Van der Waals attraction dominates, leading to a total negative pressure of about -1.074×10⁻¹² Pa with increased aggregation. Thus, our findings suggest that SiO₂ nanoparticles are more likely stable at high salinity, while Al₂O₃ nanoparticles perform better at low salinity. Moreover, this work has provided critical insights for optimizing nanoparticle selection in EOR applications to enhance stability and efficiency in varying reservoir conditions.