Comprehensive experimental study on the effect of silica nanoparticles on the oil recovery during alternating injection with low salinity water and surfactant into carbonate reservoirs

Abstract

Although the potential of nanoparticles (NPs) to improve oil recovery is magnificent, the effect of NPs during alternating injection is still vague. The main objective of this study is to investigate the best recovery mechanisms during alternating injection of NPs, low salinity water (LSW), and surfactant and transform the results into field-scale technology. The results of the laboratory coreflooding experiments, which are performed on different core plugs taken from Indiana limestone (carbonate) reservoir, are presented in this study. To determine the best recovery mechanisms, different combinations of alternating injection of silica NPs, LSW, and Sodium Dodecyl Sulfate (SDS) surfactant into the selected cores are conducted at temperature and pressure of 70 °C and 3000 psi, respectively. The experimental procedure is designed to reflect the best industrial practice for the injection of fluids into the reservoir. The outcome of these experiments revealed that the tertiary injection of NPs results in additional oil recovery beyond the limit of LSW. An additional oil recovery of 5–6% is achieved by alternating injection of NPs and surfactant after injection of LSW. Therefore, a total oil recovery of 8–11% is obtained from alternating injection of LSW, NPs, and surfactant. However, it was observed that less than 5% of the oil in place is recovered from the tertiary alternating injection of NPs dispersed in LSW and surfactant. The improvement in oil recovery is attributed to the wettability alteration, reduction in interfacial tension (IFT), and increase in the sweep efficiency. The sweep efficiency is improved by the deposited NPs, which cause the formation damage in the rock. The deposited NPs are removed by the Marangoni flow of fluid, which is activated by the injected aqueous solution. Therefore, this study has revealed that the alternating injection of NPs along with the LSW and surfactant is not only the best effective and efficient recovery mechanism but also economical for oil recovery in carbonate reservoirs.