Evaluation of Silica-Based Nanofluid Foam in Waxy Oil Recovery and Its Role in Mitigation of Surfactant Loss

The use of silica nanoparticles (SNPs) has shown promising results in providing higher foam stability in chemically enhanced oil recovery (cEOR). In this study, hydrophobic SNPs stabilized in a carboxylate anionic surfactant were selected to improve the performance of surfactant foam flooding through the sand pack experiment. The effects of SNPs on foam flooding, including foam stability, surfactant adsorption, wettability alteration, and displacement efficiency, were investigated. The results confirmed that the addition of SNPs significantly enhanced foam stability. The surfactant adsorptions onto the sand medium were reduced by 54 and 27% in the presence of SNPs at 5000 and 1000 ppm, respectively. The addition of the SNP-surfactant could alter the wettability of the oilcoated surface to water-wet conditions as probed by the contact angle measurement. The displacement efficiency reached a cumulative recovery of 97.58% original oil in place (OOIP) by the SNP foam flooding system at 1000 ppm SNPs compared to 77% OOIP obtained from the neat surfactant foam system. Gas chromatography-time-of-flight-mass spectrometry (GC-TOF-MS) analysis was adopted to characterize the incremental change in crude oil compositions at each pore volume to probe the flooding performance in correspondence with the oil properties, i.e., waxy components. As a result of combining the effects of the SNP-surfactant on improving the foam stability, surface alteration, and minimizing the surfactant loss, more available surfactants could efficiently sweep the residual waxy and heavy oil components. The findings of this study revealed an understanding of improving oil displacement of waxy crude oil by SNP-surfactant-stabilized foam, which is applicable for waxy crude oil reservoirs.