Effect of SiO2 nanoparticles on fines stabilization during low salinity water flooding in sandstones

Abstract

Low salinity water (LSW) flooding is a commonly used technique to recover remaining oil. Efficiency of this method can be improved by decreasing salinity of the injected fluid during LSW flooding. However, the environment of low salinity is unfavorable for fine-sized particles retention, and may result in fines migration and formation damage. In most sandstone reservoirs, migration and production of fines along with fluid is a major problem in oil and gas industry.Several methods can be used to control migration of fine-sized particles. One effective treatment is to use nanofluids. Nanofluids can affect surface charges and increase the attraction between the particles and sand surface. Fines are negatively charged while nanoparticles usually have positive charge. By attracting nanoparticles to surface of the sand, sand surface becomes more positive which leads to retention of fines. In previous studies, effect of nanoparticles on fines migration in aqueous media was investigated. Another parameter which can influence surface charges is presence of hydrocarbon. Crude oil is an organic substance which is negatively charged just like other organic substances. And this charge difference explains why the presence of oil can affect the performance of nanoparticles in fine migration control.The purpose of this experimental study is to investigate the effect of using SiO2 nanoparticles on controlling fines migration caused by LSW injection in presence of hydrocarbon. In addition, the effect of fine particles stabilization on oil recovery was analyzed. A mixture of paraffin and decane was used as hydrocarbon. Experiments have been conducted in three different series. The first series of experiments aimed to select the best nanoparticle among Al2O3, SiO2, and MgO. The results showed that silica nanoparticles had a great potential to control fines migration during LSW flooding. In the second series, the impact of injected nanofluid concentration on fines migration was investigated. And, in the third series, the effect of soaking times of 6, 12, 24, and 48 h was investigated. In addition, recovery of oil is measured in all tests. Silica oxide nanofluid in 0.1% wt. concentration shows the best performance in controlling fines migration and reducing the pressure drop in the porous media. In the third series of experiments, the soaking time of 24 h for the SiO2 nanofluid showed the best results for controlling fines migration. Also, our experiments showed that migration of fines cannot be considered as an effective mechanism of enhanced oil recovery during LSW flooding.