Effects of salinity on nanosilica applications in altering limestone rock wettability for enhanced oil recovery

Abstract

The role of nanoparticles in enhancing oil recovery from oil reservoirs is an increasingly important topic of research. Nanoparticles have the properties that are potentially useful for enhanced oil recovery processes, as they are solid and two orders of magnitude smaller than colloidal particles. One of the important roles of nanoparticles in petroleum industry is to change the wettability of reservoir rocks. However, there are many parameters that can affect nanoparticles applications in porous media. Parameters such as various concentrations of nanoparticles, presence of different salinities, amount of clays, type of crude oil and temperature. The main objective of this project was to investigate the efficiency of silica nanoparticles in enhancing oil recovery in the presence of formation brine with different concentrations. The methodology of this study involved several laboratory tests. It is divided into two main sections with the aim of enhance oil recovery of oil wet reservoirs. First, the wettability alteration and oil–water interfacial tension modification induced by introducing different concentrations of nanosilica (0.01, 0.05, 0.1wt%) and different concentrations of NaCl formation brine (0.3, 1, 2, 3, 4 wt%) was studied by experimental approach. Second, the displacement test for determining oil recovery for those different concentrations of nanosilica and formation brine. There exists an optimal nanoslica concentration for varying salinity and an optimal salinity for varying nanosilica concentration at which the wettability alteration on oil wet limestone is the maximum for the study. The results revealed that IFT and contact angle tests were found to have the same optimal salinity (0.3 wt%) and optimal nanosilica concentration (0.1 wt%) where by these concentrations the IFT reduced in reservoir to 12 mN/m and the lowest contact angle (53o) was obtained. Furthermore, the highest value of displacement efficiency obtained at nanosilica 0.05wt% and salinity 0.3 wt% NaCl where the reduction of residual oil saturation was less than 6 points %. As conclusion, as the salinity increases, the extent of wettability alteration, IFT reduction, and enhanced oil recovery by nanosilica decreases.