Hydrophobic effect further improves the rheological behaviors and oil recovery of polyacrylamide/nanosilica hybrids at high salinity

The study aims to improve the rheological behaviors and oil recovery of hydrolyzed polyacrylamide (HPAM) at high salinity by introducing nanosilicas . It was found that the combination of hydrophobically associating polyacrylamide (HAHPAM) and cetyl-modified nanoparticles (CMNPs) has a more substantial synergy for improving rheological behaviors of hybrid dispersions at high salinity, comparing with other HPAM/NP hybrids. The CMNPs markedly facilitate the cross-links among clumpy molecular aggregates of HAHPAM and made the hybrids more elastic. At a given HAHPAM concentration, there exists an optimal CMNP concentration at which the adsorption of nanosilicas on the polymer molecular chains is maximized. Under reservoir conditions, the HAHPAM/CMNP hybrid is more efficient than the HAHPAM/NP hybrid for enhanced oil recovery. The oil displacement mechanism of the HAHPAM/CMNP hybrid is attributed to the synergistic thickening and wettability change. The hydrophobic effect between HAHPAM and the CMNPs effectively improves the salt tolerance of the hybrids.