ABSTRACT
This paper presents the approach used for performing life extension of an aging forty two years offshore pipeline thereby providing necessary assurance for safe and continued operation. Offshore pipeline systems are susceptible to a number of damage mechanisms including but not limited to internal corrosion, external corrosion, concrete weight coat damage, excessive free spans, loss of supports and structural (third party) damage. The life extension approach identified the relevant damage mechanisms, internal corrosion modeling and evaluated the current integrity status of the offshore pipeline. This involved reviewing the available pipeline data including inspection & monitoring records, history of leaks & repairs as well as previous engineering assessments. The key findings from the integrity assessment included discrepancies in wall thickness depth measurement between the ILI results and the actual field measurements, presence of large number of external corrosion anomalies and low internal corrosion rate & flow velocity. It was recommended to utilize an advanced ILI technology capable of detecting and sizing small anomalies to overcome the limitations with currently utilized ILI technique. The external corrosion activities were attributed to ineffective cathodic protection due to shielding by disbonded coating. Furthermore, pipeline repair readiness plan was recommended to be in place considering the criticality of the pipeline. Based on the integrity assessment, determining the current condition of the offshore pipeline, it was concluded that the pipeline is currently fit for service and can continue to operate provided that the recommendations are implemented.
