Effect of Silica Nanoparticles on the Oil Recovery During Alternating Injection with Low Salinity Water and Surfactant into Carbonate Reservoirs

摘要

Application of nanoparticles(NPs)for enhanced oil recovery(EOR)has gained a lot of attention in recent years.Several laboratory studies have shown that the injection of nanofluid leads to a significant amount of oil recovery by modifying the fluid and rock/fluid properties,including the viscosity,interfacial tension(IFT),and wettability.Although the potential of 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 3,000 psi,respectively.The experimental procedure is designed to reflect the best industrial practice for the injection of fluids into the reservoir.This study also investigates the effect of silica NPs on the IFT and the wettability at aforementioned conditions.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 difference in the results is attributed to the wettability alteration by the NPs beyond the limit of the LSW and the reduction in the IFT with/without surfactant.The interpretation of the results of this study improves the understanding of the key mechanisms and the best recovery mechanisms for the application of NPs for EOR in carbonate reservoirs.