Tug-of-war between hydrogen bond and hydrophobic interaction of bisfunctionalized graphene oxide/hydrolyzed polyacrylamide allows thickening and salt-resistance in enhanced oil recovery

Polymer flooding is the most commonly used method to enhance oil recovery. Due to the harsh stratum environment, it is particularly important to prepare polymer systems with high viscosity and salt resistance. Here, we present a tug-of-war strategy that can easily control polymer system viscosity and salt resistance. By introducing hydroxyl and phenyl groups to the surface of GO, we successfully synthesized a series of Diethanolamine-Diphenylpropylamine Graphene Oxide (DDGO) with different ratio of hydroxyl and phenyl, as confirmed by TGA, ATR-FTIR and XPS analysis. 1H NMR demonstrated the three DDGOs have different phenyl/hydroxyl ratio. TEM images showed DDGO maintained 2D nanostructure upon modification. We mixed partially hydrolyzed polyacrylamide (HPAM) with DDGO to form a hybrid system. The surface hydroxyl groups of DDGOs are bridged with HPAM through hydrogen bonds to improve network structures, whereas phenyl groups are conducive to self-association by π-π interaction. The properties of the hybrid systems are regulated by the tug of war of functional groups on the surface of nanoparticles. The results from oil displacement experiments showed that the enhanced oil recovery ratio jumped to 21.5% for HPAM/DDGO system, while it was only 7.7% for HPAM solution, which provides an alternative thought of EOR.