Injection of smart water mixed with various oil-water interfacial tension (IFT) reduction agents such as nanoparticles (NPs) into oil reservoirs is a proven enhanced oil recovery (EOR) method. A novel silica-montmorilantxanthan was used to formulate novel hybrid nano-smart water solutions for EOR. Performance of the hybrid nano-smart water solutions as dispersion media at optimum salinity and NC concentrations was assessed. Stability, IFT, zeta potential, and wettability alteration of the solutions were assessed to find the optimum concentrations. Two groups of single and binary salts were used in the smart waters. Smart waters with individual NaCl, KCl, MgCl2 , CaCl2 , Na2SO4, MgSO4, CaSO4, and K2SO4 salts at concentrations of 1000, 2000, 4000, and 10,000 ppm in one group. Smart waters with a combination of each of the chlorates with various sulphates with equal ratios (1000/1000, 2000/2000, 4000/4000, and 10,000/10,000 ppm) in distilled water in another group. Smart waters with a combination of each of chlorates with various sulphates with equal ratios in distilled water in another group. Then the effects of the solution of these salts on IFT and contact angle in water-oil-sandstone and water-oil-carbonate systems were investigated. The optimum concentration of K2SO4+MgCl(2 )for the sandstone sample was determined as 1000/1000 ppm with 1000 ppm of the NC. The optimum concentration of MgSO4 for the carbonate sample obtained was 10,000 ppm with 250 ppm of the NC. The lowest IFT (15.42 mN/ m) was obtained for the nanofluid with an NC concentration of 250 ppm. The results suggest that the salt-in effect and nano-film formation are behind the IFT reduction. Contact angle at the same NP concentration decreased from 109 degrees (preferentially oil wet) to 33 degrees (strongly water-wet) in the carbonate sample. For sandstone, the contact angle at the same NC concentration increased from 77 degrees (preferentially water-wet to 117 degrees - preferentially oil wet). Finally, we used the optimum formulas for core flooding to examine the performance of the prepared hybrid nano-smart water solutions. Using these novel hybrid nano-smart waters yields oil recoveries of up to 54% and 60% of the Oil Originally in Place (OOIP) in carbonate and sandstone samples, respectively.

Nanoparticles are used in various nano-energy applications such as wettability shift of hydrophobic surfaces to hydrophilic surfaces in oil-brine-mineral systems and interfacial tension (IFT) reduction for enhanced oil recovery. This is possible due to their small size (1-100 nm) and chemical and physical properties. Mechanistically, they can interact with a fluid in the pore space and provide favourable conditions for wettability shift, IFT and oil viscosity reduction, and thus improve oil recovery. However, literature is scarce in terms of providing comprehensive information about the behaviour of nanocomposites (NCs) and associated formulations. In this paper, we present biosynthesis, characterization, and application of a novel nanocomposite (SiO2@Montmorilant@Xanthan) which is used with various concentrations (100, 250, 500, 1000, 1500, and 2000 ppm) as dispersing agents in porous media. The NC was characterized using X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Thermogravimetric Analysis (TGA), Fourier Transform Infrared Spectroscopy (FTIR), and Energy Dispersive Spectroscopy (EDS). The effects of different concentrations of the nanosuspensions on zeta potential, pH, conductivity, IFT, and wettability are investigated. Core flooding tests were done on sandstone and carbonate reservoir rocks to measure the secondary and tertiary recovery potential by injecting seawater and optimum NC concentrations, respectively. Zeta potential and conductivity experiments demonstrated that 250 ppm NCs can optimally reduce the IFT from 36 mN/m to 15.42 mN/m (56% reduction). The similar optimum concentration has shifted the wettability of examined carbonate rocks from 150 degrees to 33 degrees leading to an 11.72% increase in tertiary oil recovery. Whereas, the optimum concentration of NCs for sandstone rocks was 1000 ppm; which, has optimally altered the wettability from 140 degrees to 34 degrees, and has increased the tertiary oil recovery by 15.79%. This reduction in IFT, the reversal of wettability, and an increase in tertiary oil recovery can improve significantly the design of effective enhanced oil recovery schemes for petroleum reservoirs.

In this paper, synthesis and characterization of a novel CeO2/nanoclay nanocomposite (NC) and its effects on IFT reduction and wettability alteration is reported in the literature for the first time. The NC was characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), energy-dispersive X-ray spectroscopy (EDS), and EDS MAP. The surface morphology, crystalline phases, and functional groups of the novel NC were investigated. Nanofluids with different concentrations of 100, 250, 500, 1000, 1500, and 2000 ppm were prepared and used as dispersants in porous media. The stability, pH, conductivity, IFT, and wettability alternation characteristics of the prepared nanofluids were examined to find out the optimum concentration for the selected carbonate and sandstone reservoir rocks. Conductivity and zeta potential measurements showed that a nanofluid with concentration of 500 ppm can reduce the IFT from 35 mN/m to 17 mN/m (48.5% reduction) and alter the contact angle of the tested carbonate and sandstone reservoir rock samples from 139° to 53° (38% improvement in wettability alteration) and 123° to 90° (27% improvement in wettability alteration), respectively. A cubic fluorite structure was identified for CeO2 using the standard XRD data. FESEM revealed that the surface morphology of the NC has a layer sheet morphology of CeO2/SiO2 nanocomposite and the particle sizes are approximately 20 to 26 nm. TGA analysis results shows that the novel NC has a high stability at 90 °C which is a typical upper bound temperature in petroleum reservoirs. Zeta potential peaks at concentration of 500 ppm which is a sign of stabilty of the nanofluid. The results of this study can be used in design of optimum yet effective EOR schemes for both carbobate and sandstone petroleum reservoirs.