Failure Analysis of Shale Gas Sewage Pipeline

To solve the problem of thinning of the wall thickness of the sewage pipeline on the side of the shale gas separator of Sichuan E Oil and Gas Field Company, this study explores the reasons for the failure of sewage pipelines by macroscopic inspection, mechanical property experiment, metallographic structure analysis, (electron microscope scanning) SEM, (energy-dispersive spectrometry) EDS, (X-ray polycrystalline diffractometer) XRD, and CFD simulation analysis. Inspection found corrosion on the weld seam and inner wall surface of the pipeline. The elements in the corrosion products are mainly C, O, Fe, and Cl, and the corrosion products are mainly FeCO₃. Therefore, one of the causes of pipeline failure is CO₂ corrosion. Cl^- exists in the transportation medium of the pipeline, which promotes CO₂ corrosion under the action of acidification and autocatalysis; CFD simulation analysis found that the erosion of pipeline by grits is concentrated at the diameter change location of the pipeline, which is the same as the location of corrosion. Therefore, the cause of pipeline failure is the combined effect of CO₂ corrosion and grits erosion.