On-line inspection of pipelines using intelligent pigs constitutes a major aspect of corrosion control programs. The policy established by a petroleum operator is presented. It defines when base-line and early
inspection surveys are considered necessary. The paper discusses the pros and cons of intelligent pigging operations and gives guidelines for deciding when to run in-service inspections to assess the condition of a
pipeline and to verify the efficiency of corrosion control measures on a long term basis. H highlights factors like the estimated maximum corrosion rate, the positive change of actual corrosion allowance with time and the detection limits by the selected intelligent pigs. In the second part, a recent experience concerning the base-line survey of the Lille-Frigg 10“ wet gas production pipeline in the North Sea using an ultrasonic pig is presented. The inlet of this pipeline is situated at a subsea manifold. The third part of the paper discusses aspects of intelligent pigging where difficulties are found and where improvements or new technological developments are needed.
Keywords: intelligent pigs, on-line inspection, pipelines, CO2 corrosion, subsea manifold, corrosion control program, base-line survey, early inspection suwey, condition assessment sutvey, ultrasonic pigs.