Study on the Corrosion Mechanism of Low-Lying Area of Gathering Pipeline in Daniudi Gas Field
To investigate the corrosion mechanisms of low-lying areas in the gathering and transportation pipelines of the Daniudi Gas Field,the distribution of accumulated liquid along the pipeline was simulated.A low-lying section of the pipeline located 1207 m from the starting point was identified as the primary monitoring point.Excavation of pipeline sections and installation of coupons were conducted on-site.Weight loss testing was used to calculate the corrosion rates of the coupons,and the microscopic structure and composition of the corrosion products were characterized using scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS) and X-ray diffraction(XRD) .Results showed that the uniform corrosion rate of the coupons at the gas tree was 0.0035 mm/a,the corrosion degree was slight,and no obvious local corrosion tendency was observed.The uniform corrosion rate of the low-lying coupon was 0.0599 mm/a,the local corrosion rate was 0.1380 mm/a,the pitting corrosion coefficient was 2.3,and the degree of localized corrosion was severe.The structure of the corrosion products on the surface of the low-lying pipe samples was loose,and the corrosion products were mainly composed of FeCO3,FeS and Fe2O3 .It was speculated that the corrosion was mainly caused by the corrosive gases CO2 and H2S,with Cl-in the effluent playing an accelerating role.
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