Abstract
In this paper a methodology to assess the risk of internal corrosion for a large gas gathering, transmission and distribution piping network is proposed. Due to the high number of pipelines present in the system, performing internal corrosion direct assessment (ICDA) for all the gas pipelines appears to be unrealistic and unfeasible. Therefore, an approach based on phase-envelope analysis for the transmitted gas is proposed to determine the water carrying capacity of the flow and also to flag pipelines which are susceptible to water condensation and drop-out based on their operational conditions. This approach will serve as a screening step to identify the pipelines which require a more detailed corrosion risk assessment such as full ICDA, pressure test or inline Inspection (ILI). In addition, the effect of heavy hydrocarbon gas molecules (C6+) on the shape of the hydrocarbon phase envelope is investigated and the probability of forming a liquid hydrocarbon phase is evaluated.
Obtained results highlight the importance of performing reliable gas analyses at different locations in a large piping network, especially at regions close to the compressors or the gas dehydration units, and demonstrate the success of the proposed approach to systematically investigate the risk for internal corrosion for a large gas transmission, distribution network during different operational seasons.
