Detection Of The Residual Concentration Of Imidazoline Inhibitors In Oilfield Production Water

Corrosion inhibitors have been widely applied in oilfield exploration processes. Theaccurate measurement of their residual concentrations has a great significance to theirpractical application, control of their implantation technique, as well as the development ofnew inhibitors.In this study, UV-visible absorption spectroscopy, fluorescence spectroscopyand cyclic voltammetry were applied to detect the residual concentration of imidazolineinhibitors in oilfield production water.The method of UV-visible absorption spectroscopy was applied to detect the residualconcentration of imidazoline inhibitors. The results show that imidazoline and itsderivatives have the maximum absorption wavelength at235nm. In a certain range ofconcentrations, the absorbance shows the positive linear relationship with the imidazolineconcentration, and then, its concentration can be detected by UV-visible absorptionspectroscopy method at pH=4-10. The influence of color reagents including cresol red,bromocresol purple, congo red and bromothymol blue on UV-visible spectra forimidazoline inhibitors is studied. The influence of K⁺，Na⁺，Ca²⁺，Cl-，HCO₃^-，SO₄^2-，HPO42-，Mg²⁺and Fe3+is researched. All the results prove that without any pretreatment tothe production water the residual concentration of midazoline inhibitor can be in-situdetected accurately by UV-visible spectroscopy method.When fluorescence spectroscopy was applied to detect the residual concentration ofimidazoline inhibitor, the results show that imidazoline and its derivatives havefluorescence peak at445nm when be excited by the light. In a certain range ofconcentrations, the fluorescence intensity have a linear relationship with the inhibitorconcentration. Therefore the method of fluorescence spectroscopy for quantitative analysisof imidazoline inhibitor is feasible. We find out a suitable fluorescent agent Eosin Y whichhave fluorescence peak at550nm after reacted with imidazoline inhibitor. And thefluorescence intensity have a good linear relationship with the inhibitor concentration. Thereaction mechanism for Eosin Y and imidazoline corrosion inhibitor is analyzed.The method of cyclic voltammetry was applied to quantify the concentration of imidazoline inhibitor. In a certain range, cyclic voltammetry can determine theconcentration of imidazoline inhibitor within a short range, but can not quantify itaccurately.