Experimental studies on effectiveness of graphene oxide nanosheets dispersion in water/aqueous PHPA for enhanced oil recovery

Nanoparticle application in enhanced oil recovery is emerging as a novel technology because of their unique characteristics, viz. reduction of IFT, wettability alteration, and stable dispersion in injection water and aqueous polymer solution. In the present study, graphene oxide nanosheets (GONs) are synthesized by modified Hummer's method. The nanosheets are characterized by FTIR, XRD and UV-vis spectroscopy analysis. The size of the nanosheets was confirmed by the AFM and HR-TEM imaging. The stability of nanofluid (NF) with dispersed GONs in the aqueous solution was confirmed by Turbiscan stability analysis, DLS studies and zeta-potential values (less than -34 mV). The experimental research reveals that NF alters the wettability of intermediate oil-wet sandstone reservoir rock with a reduction of contact angle from 112.4 degrees to 17.2 degrees. Further, it is observed that the IFT between oil (decane) and deionized water decreases from 42.34 mN/m to 32.76 mN/m for the NF system. It has been observed that the synthesized GONs can emulsify crude oil, which is also an important mechanism of EOR. The rheological studies show that GONs enhance the viscosity and viscoelastic properties of partially hydrolyzed polyacrylamide (PHPA) polymer. GONs form a robust three-dimensional network structure facilitated by hydrogen bonding with the PHPA polymer chain, which leads to the improvement of sweep efficiency. The core flooding experiment demonstrates that the incremental oil recovery over the conventional water flooding by GONs dispersed in the PHPA polymer with flooding is significantly higher (26% of original oil in place) than that of individual NF and polymer flooding.