Research on corrosion perforation on pipeline by media of high salinity acidic oil–water mixture

Corrosion perforation and scaling occur frequently in pipeline of Tuha oil field. After being exposed to crude oil in petroleum transmission pipeline for 120 days, corrosion rate of weight loss of the steel disc was calculated. Scanning Electron Microscope (SEM) was employed to observe the microscopic corrosion morphology of coupon, and the compositions of the oily water mixture and pipes were analyzed. The microstructure of the corrosion products and the reason of corrosion were investigated by Energy Dispersive Spectroscopy (EDS) and X-ray Diffraction (XRD). The result showed that non-uniform corrosion occurred on the surface of coupon, and corrosion rate of weight loss was 0.187 mm/y The corrosion products was mainly ferrous sulfide (FeS) and silicon disulfide (SiS2), and the scaling was mainly calcium carbonate (CaCO3). The corrosion-cell reaction, calcium ion (Ca2+) and bicarbonate ion ( HCO 3 - ) in formation water, and sulfuretted hydrogen (H2S) were the major factors which caused pipeline corrosion and scaling. H2S and Ca2+ weakened carbon dioxide (CO2) corrosion of pipeline in oil–water mixture medium.