Major corrosion factors in the CO2 and H2S coexistent environment and the relative anti-corrosion method: Taking Tazhong I gas field, Tarim Basin, as an example

Anti-corrosion techniques are studied to deal with the CO2 and H2S coexistent environment of the Tazhong I gas field. Orthogonal experiment with five different factors and levels is carried out to compare the influence of the factors on the corrosion rate of the sulfur-resistant tubing. These five factors are pressure of CO2, pressure of H2S, temperature, content of Cl−, and water cut. It is found that CO2 pressure is the major corrosion factor. The combination of sulfur resistance tubing and corrosion inhibitor is selected as the anti-corrosion method and the proper corrosion inhibitor named YU-4 is designed according to the result of orthogonal experiment. This anti-corrosion method was used in 12 wells of the Tazhong I gas field, achieving good results. The average corrosion rate of Well TZ83 decreased from 1.23 mm/a to 0.025 mm/a and the corrosion rate of Well TZ623 decreased from 0.370 mm/a to 0.016 mm/a. Key words: gas well, CO2, H2S, corrosion, influencing factor, major factor, anti-corrosion metho