Preparation And Mechanism Research Of Corrosion Inhibition System For Coiled Tubing Pickling In Gas Well

The pickling operation effectively solved the plugging problem of gas wells with coiled tubing in the Puguang Gas Field.However,the pickling solution caused serious corrosion to the coiled tubing due to the harsh H₂S/CO₂ corrosion environment,which greatly affected the safety and service life of the coiled tubing.Therefore,the development of efficient corrosion inhibitors is crucial for oil and gas field production.According to the corrosion environment of Puguang Gas Field,the corrosion inhibition performance of corrosion inhibitors currently used for coiled tubing was evaluated in high acid environment,in which static corrosion rate was adopted as the most important evaluation index,based on the high temperature and high pressure corrosion resistance equipment.And the best optimal formulation of corrosion inhibitors and synergists?1.2wt.%imidazoline quaternary ammonium+0.6wt.%CBS-HA+0.1wt.%urotropine?was determined through a compounding experiment.The formula could reduce the corrosion rate to 11 g·m^-2·h^-1 and meet the first-class standard.In addition,an urotropine quaternary ammonium salt corrosion inhibitor was synthesized in this paper,synthetic conditions were optimized through orthogonal experiment,in which static corrosion rate was adopted as the most important evaluation index in 15%HCl solution at 90?,and the corrosion inhibition performance and compounding performance of the synthetic corrosion inhibitor was studied.Through the compounding experiment,an efficient corrosion inhibitor system is finally obtained using quaternary ammonium urotropin as the main component.The corrosion inhibitor system could reduce the corrosion rate to 8g·m^-2·h^-1 in the corrosive environment of Puguang Gas Field and superior to the first-class standard.The mechanism of corrosion inhibitors was studied by polarization curve,electron microscopy,electron energy spectrum.Electrochemical experiments indicated that the imidazoline quaternary ammonium salt and synergistic inhibitior were mixed inhibitor which works mainly by preventing or slowing down the anodic reaction.The imidazoline quaternary ammonium salt and synergistic inhibitior molecules could adsorb on the surface of QT-800 steel through the SEM and EDS analysis and corrosion inhibitor molecules could form a protective film on the metal surface inhibit the H⁺close to the metal surface to achieve the purpose of inhibiting corrosion.In addition,the quantitative parameters of the urotropin quaternary ammonium salt corrosion inhibitor were analyzed by the Dmol³ module in the Materials Studio.The Forcite module was used to analyze the kinetics of urotropin quaternary ammonium salt and further understand the corrosion inhibition mechanism of the urotropin quaternary ammonium salt corrosion inhibitor.