Challenges in Managing Top of Line Corrosion TLC in Multiphase Wet Gas Pipelines

Abstract

Top of Line corrosion (TLC) has becoming a growing concern for the oil and gas industry over the past recent decades especially on the offshore subsea high temperature and high pressure (HTHP) pipelines. This paper will present the challenges in managing TLC in multiphase wet gas pipelines. It will also cover the design, execution, appropriate inspection and corrosion monitoring to ensure pipeline integrity meeting the intended design life. There are many corrosions prediction modelling softwares available in the open market. However, once TLC is predicted in a pipeline, there are only few mitigation options which are by material selection, chemical injection, routine operation pigging, batch inhibition, etc. New projects are often considering material selection to mitigate TLC. This approach is rather straight-forward, however, high CAPEX is required. As for existing pipelines in operation with TLC, it must depend on effective chemical control (corrosion inhibitor) that could protect both TLC and BLC (bottom of line corrosion) coupled with continuous corrosion monitoring tools. Routine pigging during operation and more frequent inspection could be required too. To date, there is no common standard in testing the effectiveness of volatile corrosion inhibitor (VCI) in mitigating TLC.