An internal corrosion failure occurred in one of Shell Canada’s (Shell) high density polyethylene (HDPE) lined sour gas pipelines in 2007. That failure led Shell to shut in all of its lined sour gas pipelines until the integrity of each could be verified and the internal corrosion mechanism was under control. The presence of a non-metallic liner within the pipelines made full in-line inspections (ILI) challenging.
The removal and re-installation of liners had been the typical way to complete such ILI with magnetic flux leakage (MFL) smart pigs, but this was not practical in this case. Existing remote field testing (RFT) ILI tools were available and had been used by industry to inspect unlined pipelines, reinforced-concrete and cement mortar lined (CML) pipelines.
It was this technology that was chosen to inspect the lined sour gas pipelines with the liners in place. The use of repeat RFT ILI since 2008 has provided verification of integrity and confirmed the pre-existing internal corrosion mechanism is now under control.
The inspection success with HDPE lined pipelines led Shell to use the same technology to recently inspect a 28yr old CML produced water pipeline. External corrosion at disbanded coating locations was confirmed active on the pipeline. The RFT ILI allowed Shell to schedule repairs and continue use of the CML pipeline.
The ability to ILI existing lined pipelines without removing the liners is a tremendous advantage to Shell. RFT ILI of lined pipelines was novel in the past but is now considered a normal practice. This paper summarizes the experience and shares the learnings of the successful application of RFT ILI technology, which became an important part of Shell’s pipeline integrity management program.