Research On Pitting Corrosion And Anti-corrosion Of Oil Tube Under High Content Of Cl^- And H₂S-CO₂ Fluid

With the continuous development of the oil fields which have high content of Cl-and H2S-CO2,many problems appeared during oil production.One of the critical problems is the pitting corrosion of oil tube under high content of Cl-and H2S-CO2 fluid.The pitting corrosion of oil tube cause not only the economic loss,but also the environmental issues and safety issues,so the research on pitting corrosion and anti-corrosion of oil tube under high content of Cl-and H2S-CO2 fluid is very important.This thesis researched the corrosion rate based on different corrosion conditions of Clcontent,H2 S content and CO2 content using the Rotating Coupon Apparatus,the High-temperature and High-pressure Coupon Tester and Dynamic Coupon Test Loop which was built to establish the actual production status.The test conditions were designed to cause the coupons to occur pitting corrosion,and then the anti-corrosion performance of the Imidazoline Corrosion Inhibitor was researched.The mechanisms of pitting corrosion and anti-corrosion were studied.The anti-corrosion process was proposed.The Electrochemical Workstation was used to evaluate anti-corrosion performance of four kinds of carbon steel,one kind of low-alloy steel and four kinds of alloy steel.The material selection method was optimized.The research results show that the corrosion rate increases with the salinity increasing.The flow rate has significant impact on corrosion rate.The hydrogen sulfide increases the corrosion rate at about 40% in salty fluid,and the carbon dioxide increases the corrosion rate at about 30% in salty fluid.The Imidazoline Corrosion Inhibitor can decrease the corrosion rate effectively for carbon steel.The pitting corrosion can be controlled when the anti-corrosion rate of corrosion inhibitor achieves a certain level.The corrosion resistance of alloy steel is significantly better than carbon steel and low alloy steel.The corrosion rate of alloy steel is 1~2 orders of magnitude lower than the low alloy steel and carbon steel in same experimental medium.Using the alloy steel is the optimized material selection method for pitting corrosion resistance.