Corrosion Failure Analysis of Offshore Oilfield Wellhead Pipe Welds

An offshore oilfield wellhead crude oil pipeline system leaked locally, and the leaking locations were near the welds of the pipelines. A typical sample was taken from the leaked pipes and the sample was analyzed by means of macro examination, tests of chemical and mechnical properties, X-ray diffraction(XRD), microstructure examination, energy-dispersive spectroscopy(EDS) and assessment of grooving corrosion to find out the corrosion and leakage reason. The results show that the reason of the pipeline corrosion was wet CO2 corrosion, and the grooving corrosion promoted and accelerated the whole corrosion process. Some protective measures were proposed according to the corrosion analysis results.