Development of Graphene <scp>Oxide@Hyperbranched</scp> Polyglycerol Nanofluids for Application in Enhanced Oil Recovery

ABSTRACT The development of graphene oxide (GO)‐based nanofluids presents a promising strategy for enhanced oil recovery (EOR), given GO's potential to alter rock wettability and interact with oil and reservoir surfaces. This study explores the synthesis, functionalization, and application of GO nanofluids for EOR. GO nanosheets were prepared with varying oxidation levels using the Hummers method and functionalized with anionic or cationic surfactants and hyperbranched polyglycerol (HPG) to improve dispersion stability. Stability in water and brine with controlled salinity was assessed via zeta potential measurements. Contact angle analyses evaluated wettability changes on aged calcite and glass surfaces. Raman spectroscopy and atomic force microscopy provided insights into the nanofluid–rock interaction mechanisms. Oil displacement tests were performed in porous media packed with limestone and sandstone. Results showed that GO nanofluids significantly enhanced oil recovery over conventional methods, particularly when modified with HPG and dispersed in sulfate‐rich, controlled‐salinity water. The best system recovered 19% of the residual oil from limestone, highlighting the importance of nanofluid composition and stability for optimizing EOR performance. These findings suggest that tailored GO‐based nanofluids hold substantial potential for improving oil recovery in challenging reservoir conditions.