The impact of silica nanoparticles on the performance of polymer solution in presence of salts in polymer flooding for heavy oil recovery

Due to role of polymer in increasing sweep efficiency during oil recovery, much attention has been paid to the using polymer solutions in enhanced oil recovery methods. In spite of the existence of the great researches in this area, the role of nanoparticles in modification of the polymer performance in the presence of salts has not been examined before. Furthermore, there is no information about how the dispersed silica nanoparticles affect the heavy oil recovery during the polymer flooding in the presence of divalent cations. In this study, a series of polymer flooding experiments are performed in a quarter five-spot glass micromodel saturated with heavy oil. Solutions of polyacrylamide and dispersed silica nanoparticles in polyacrylamide (DSNP) with different salinities are used as the injectants to examine the effect of silica nanoparticles on the polyacrylamide performance in the presence of salts during polymer flooding of heavy oil, the oil recovery values were measured in different salinities. Furthermore, viscosity measurements are performed to help analyzing the results of polymer flooding tests. The oil recovery is measured via analysis of the continuously captured images during the displacement. Also, microscopic monitoring is used to analyze the distribution of residual heavy oil and polymer solution at the pore level. The results showed that the oil recovery decreases by increasing the salt concentration during the polyacrylamide flooding whereas in case of flooding with suspension of silica nanoparticles in polyacrylamide, decreasing rate in oil recovery is lower. The results of viscosity measurements showed that increasing the salt concentration lowers the viscosity of polyacrylamide solution to a minimum value which at higher values salts had a reverse effect and increased solution viscosity. Moreover, viscosity of silica nanosuspension in polyacrylamide was higher than that of polyacrylamide solution at the same salinity. This increase in viscosity becomes more noticeable by increasing the silica nanoparticles concentration. Finally oil recovery values versus injectant viscosity were plotted for different condition of salinity which confirmed the previous results, it means oil recovery was increased wherever injectant viscosity has been increased.