Assessment of the remaining life of subsea pipelines based on in-line inspection results

UDK: 622.692.4.076

DOI: 10.24887/0028-2448-2026-4-112-115

Key words: subsea pipeline, internal corrosion, in-line pipeline cleaning, in-line pipeline inspection

Authors: V.V. Savelev (Vietsovpetro JV, the Socialist Republic of Vietnam, Vung Tau); I.A. Gorkov (Vietsovpetro JV, the Socialist Republic of Vietnam, Vung Tau); A.N. Ivanov (Vietsovpetro JV, the Socialist Republic of Vietnam, Vung Tau); A.S. Avdeev (Vietsovpetro JV, the Socialist Republic of Vietnam, Vung Tau)

On time steel pipelines corrosion defects detection is one of the key factors ensuring the reliable and safe operation of main subsea pipelines. This article presents the results of internal cleaning (pigging) and in-line inspection (ILI) performed to assess the remaining life of subsea pipelines operated by Vietsovpetro JV. It should be noted that the selected subsea pipelines have been in service for more than 25 years, exceeding their design life, pigging and ILI were carried out for them for the first time. A brief description of the methodological approach used for the analysis of ILI data is provided. The calculation procedure is based on the practical recommendations of DNV-RP-F101 and employs a three-level approach: selection and analysis of residual wall thickness based on ILI data; assessment of residual strength for each defect; and assessment of residual strength for clusters (groups of interacting defects). It was found that despite the long service life of the pipelines, more than 85 % of all defects is within the category of up to 40 % metal loss and are not critical. The most hazardous detected defects are located on the above-water parts of the vertical pipeline sections (risers) and are generally formed as a result of atmospheric corrosion. The study identified the differences in the chemical composition of solid deposits in oil gathering, gas-lift, and water injection pipelines. Spatial distribution features of corrosion defects in subsea pipelines were established depending on the transported fluid and its conditions.

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