Experimental study on using SiO2 nanoparticles along with surfactant in an EOR process in micromodel

Abstract

Surfactant flooding is a common chemical method for enhancing oil recovery. Recently, the simultaneous application of nanoparticles and chemical substances has been considered for improving the efficiency of EOR processes. In the present study, the microscopic and macroscopic efficiency of oil recovery in a linear micromodel in three injection cases of Sodium dodecyl sulfate (SDS) as an anionic surfactant, SiO2 nanoparticles, and simultaneous injection of nanoparticles and surfactant was investigated. In our study, adding the nanoparticles along with SDS (2000 ppm) decreased Interfacial tension by 84%, while the figure was 74% and only 10% when the surfactant and the nanoparticles were used alone, respectively. Seemingly, although the nanoparticles alone could not reduce IFT values, adding them to surfactant solution could strongly decrease the interfacial tension between oil and water, leading to enhancement of oil recovery. However, our findings showed that an optimum concentration of nanoparticles in surfactant solution must be used. In this regard, in low concentrations of nanoparticles, they were attached to the interface and IFT decreased due to absorption process. Nevertheless, in high concentrations, nanoparticles removed the surfactant from aqueous phase resulting in no free surfactant available in the bulk. Therefore, surfactant effectiveness in reducing IFT and alteration wettability decreased, and as a consequence, oil recovery efficiency dropped compared to lower nanoparticles’ concentrations. Moreover, the results of sessile drop experiments and wettability measurements revealed that coating with either the surfactants or the nanoparticles could partially alter the wettability of surface to water-wet, while coating with the surfactants along with the nanoparticles could make a strongly water-wet surface. Seemingly, investigating the microscopic images of pores and throats showed a strong water-wet condition when the surfactant along with the nanoparticles was used. In addition, the results of flooding tests demonstrated that adding the nanoparticles to surfactant solution could increase the ultimate oil recovery significantly. Moreover, microscopic images confirmed that adding the nanoparticles to the surfactant solution can lead to forming oil-in-water and water-in-oil micro-emulsions due to ultra-low IFT. Obviously, this can result in improving the effectiveness of injection fluid to influence a wider range of porous media. Keywords: SiO2 nanoparticle, EOR, IFT value, Surfactant solution, Wettability, Micro-emulsions