Effect of asphaltene on the emulsions stabilized by graphene oxide: A potential application of graphene oxide in enhanced oil recovery

In this research, graphene oxide (GO) is used to prepare stable Pickering emulsions in chemical flooding for enhanced oil recovery (EOR). The effects of GO concentration (0–7 mg/mL), salinity of aqueous phase (0–10 wt%), and asphaltene concentration in organic phase (0–2 wt%) on the stability and morphology of the emulsions are examined. Moreover, the influence of these independent variables on the interfacial tension (IFT) between organic and aqueous phase is assessed through response surface methodology. The results show that the concentrations of GO and asphaltene have the most significant effect on the IFT; indeed, the IFT reduces with increasing both GO and asphaltene concentrations. Defining two quantitative indexes make it possible to compare the efficiency of emulsions formation (ESVI) and the stability of formed emulsions during time (ESTI) against creaming at different conditions. The maximum reported values for the ESTI and ESVI are 100% and 70%, respectively. In all conditions, the type of emulsions is oil-in-water (O/W) which is more suitable in EOR. However, water-in-oil emulsions (W/O) are observed at asphaltene concentrations higher than 1.5 wt%. For dominating this phenomenon, the water/oil ratio should be increased. At the presence of asphaltene and salinities higher than 1 wt%, some water-in-oil-in-water (W/O/W) multiple emulsion droplets are observed. The minimum of the reported average droplet size is 0.69 μm for GO concentration of 1 mg/mL and asphaltene concentration of 0.05 wt%. These results demonstrate the potential applications of graphene based functional materials for EOR.