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|a The oil production has kept depleting due to several factors including the limitations of the conventional methods to recover the oil. This leads to the first problem statement on how to overcome the limitations of typical polymer flooding. Recently, nanoparticles have gained attention for their potential in accessing pores restricted for typical methods and lower down interfacial tension (IFT), which generate a stable emulsion as well as wettability alteration. Besides, the performance of Xanthan Gum (XG) in polymer flooding to enhance the oil recovery is believed to be improved with the presence of Silica Oxide (SiO2) nanoparticles. However, the effect of this synergy injection on the oil recovery has to be studied. Therefore, the objectives of this study are to evaluate the capability of the synergised XG and SiO2 nanoparticles solutions to improve the solution viscosity, IFT reduction and to analyse the effectiveness of the synergy on recovery factor improvement. The samples were being prepared with 4000 ppm XG and five different concentrations of SiO2 nanoparticles (1000, 3000, 5000, 7000 and 9000 ppm). The samples were tested for viscosity and IFT reduction to determine the optimum concentration of the synergized solution. Lastly, the flooding test was conducted by using a sand pack to measure the oil recovery factors when different slug ratios of the polymer and brine were injected. All tests were conducted at 27°C. Based on the results obtained, the viscosity of the solution is increased with the increasing SiO2 concentrations. The viscosity of the solution is increased from 27.185 up to 145.87 cp when 9000 ppm SiO2 nanoparticles were added. The synergy has shown the IFT reduction from 75.5 mN/m to 55 mN/m with the increasing concentrations of the SiO2 added into polymer solution. Thus, 4000 ppm of XG synergised with 3000 ppm SiO2 nanoparticles was chosen as the optimum concentration as the IFT reduction is achieved and can be correlated with the viscosity result. There is only a slight viscosity difference is observed when 5000 ppm SiO2 nanoparticles were added as compared to 3000 ppm SiO2 nanoparticles. The oil recovery was increased from 27.5% to 56% by using 4000 ppm XG while, the oil recovery was increased to 57.5% by using the synergized solution with similar slug ratio. The maximum oil recovery was 66.3% by using optimum synergized solution with the highest slug ratio of 50:50 polymer flooding to water slug. In conclusion, these results have proven that SiO2 nanoparticle is able to helps polymer flooding to improve both sweep and displacement efficiency by viscosity increment and IFT reduction in order to increase the oil recovery.
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