Assessment on the inner corrosion of submarine pipeline in Xijiang Oilfield

Comprehensive evaluation on the inner corrosion submarine pipeline in Xijiang Oilfield was carried out with SEM, EDS and XRD technology. Results showed that the corrosion products in accumbent straight section was relatively loose without cracks, however the corrosion products in runout section, bending section and straight section appeared a mud state along with different cracking forms. The deepest corrosion pit was concentrated upon the accumbent straight section and straight section, while the deepness of the corrosion pit in runout section, inner arc and outer arc was shallow with large lateral extension. The inner corrosion mechanism and anti-corrosion capacity of the submarine pipeline were discussed. The impact factors of flowing status, wax content and condensate water on the submarine pipeline were also studied. Results showed that the CO₂ corrosion for the submarine pipeline was a main corrosion form in service life, and the uniform thinning rate and local corrosion rate were in the range of mild corrosion and moderate corrosion. It is demonstrated that the submarine pipewline has a good performance in corrosion resistant ability.