Corrosion Behavior of Carbon Steel in Multiphase Time-Sharing Flow Sewage System

Abstract

Single well output is poor in several Yanchang oilfield development blocks, water content is high, and hydrogen sulfide is present at the same time. The tank corrosion in the on-site multiphase time-sharing flow sewage system was severe. The coupon method was used to test the corrosion rate and the scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD) methods were used to study the corrosion morphology of the coupon and analyze the composition of the corrosion products in order to effectively inhibit corrosion in the storage tank and analyze the physical and chemical properties of the sewage. The corrosion rates of the upper, middle, and lower sections of the incoming water tank increased and subsequently decreased, whereas the corrosion rates of the upper, middle, and lower parts of the filtered water tank decreased. Local corrosion, pitting corrosion, and pit corrosion were observed in the storage tank, with the corrosion products mostly being Fe2O3, FeS, and FeS2. It was determined that the primary corrosion causes in the top section of the carbon steel storage tank were dissolved oxygen and Cl−, sulfur (H2S) and SRB, and SRB in the bottom part. The combination of bacterial, hydrogen sulfide, and oxygen corrosion created the corrosion process.