A fuzzy logic-possibilistic methodology for risk-based inspection (RBI) planning of oil and gas piping subjected to microbiologically Influenced corrosion (MIC)

Abstract

The oil and gas installations are associated with risk due to different degradation mechanisms. Microbial Influenced Corrosion, commonly known as MIC, is one of them. The failures caused by MIC may have significant impacts on health, safety and environment (HSE). Therefore, to avoid failures regular inspection of the assets and maintenance plans need to be executed. With this on mind, engineers try to develop efficient inspection plans, which could form a basis for saving the assets. The different models so far developed for the assessment of MIC still have shortfalls. This might be due to the complexity of corrosion mechanisms. A model containing all the influential parameters causing MIC is difficult to develop due to the complexity of process and lack of data. Aim of this project is to develop a simple yet flexible methodology to estimate the time for inspection. The methodology contains four sections: (a) estimation of possibility of MIC initiation and stable pit growth based on a simple flowchart; (b) estimation of rate of corrosion based on Fuzzy Logic; (c) estimation of possibility and necessity of failure in the event of MIC initiation and stable pit growth based on possibilistic framework; and (d) estimation of time for inspection based on matrix. It is expected that the developed methodology would aid engineers make efficient inspection programs based on the concepts of risk-based inspection (RBI).

Keywords: MIC, Fuzzy Logic, failure, oil and gas pipes, possibilistic approach, reliability, structural integrity