Analysis on Chemical Properties of Modified Nanofluids and Their Effectiveness in Improving Oil Recovery
Nano SiO2 particles were prepared from sodium silicate and concentrated sulfuric acid,and their surface was modified with silane coupling agent KH792.The structure was characterized and analyzed using Fourier transform infrared,X-ray energy dispersive spectroscopy,SEM and thermal analysis methods.The physical and chemical mechanisms of oil recovery were analyzed,and the influence characteristics of modified nano SiO2 on the process of permeation recovery were studied.The results showed that KH792 could successfully graft onto nano SiO2,and the modified nanoparticles remained uniformly size at around 28 nm,with a particle size range of 10～60 nm.This indicated that organic chains and active groups—CH3 could effectively inhibit the aggregation phenomenon of the nanoparticles themselves.High mass concentration of nano SiO2 significantly affected the wettability of rock surfaces,reducing the interfacial tension between oil and water to 1.542 mN·m-1.As the mass concentration of nanofluids increased from 300 mg·L-1 to 1 800 mg·L-1,the infiltration recovery rate could increase from 9.96%to 34.36%.The effect of modified nano SiO2 fluid on the infiltration recovery rate increased with the increase of system permeability,temperature,mineralization degree,and pH.
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