On the impact of Co3O4 nanoparticles on interaction of heavy oil and brine mixtures

Among numerous EOR methods, the injection of brine with different salinities to oil reservoirs has gained attention where its performance would, in turn, depend on interfacial tension (IFT) of oil/brine mixture. The present study investigated the impact of Co3O4 nanoparticles with concentrations of 0.01, 0.1 and 1 wt% on IFT of brine solution (containing NaCl, KCl and CaCl2) and heavy crude oil system. The results confirmed that adding Co3O4 nanoparticles to water, compared to that without nanoparticles, reduced IFT at low (i.e. 0–5000 ppm) and high (i.e. greater than 5000 ppm) brine concentrations, although the propensity of IFT is different for various concentrations. Furthermore, the reduction of IFT for monovalent ions is greater than that for divalent ions. Properties such as high surface activity and higher surface to volume ratio of the Co3O4 nanoparticles should be accounted for profound adsorption of asphaltene onto the surface of nanoparticles. A high suspension of asphaltene at the brine/oil interface also avoided its precipitation in oil causing IFT to reduce in brine/crude mixtures with nanoparticles compared to that without nanoparticles. The extent of IFT reduction changed by using different concentrations of Co3O4 nanoparticles. For the oil/brine system attempted in this study, the optimum concentration of Co3O4 nanoparticles in term of IFT reduction was 0.1 wt%.