Risk-based Reliability Assessment of Subsea Control module for Offshore Oil and Gas production

摘要

Offshore oil and gas exploitation is principally conducted using dry or wet treesystems, otherwise called the subsea Xmas tree system. Due to the shift todeeper waters, subsea production system (SPS) has come to be a preferredtechnology with attendant economic benefits. At the centre of the SPS is thesubsea control module (SCM), responsible for the proper functioning andmonitoring of the entire system. With increasing search for hydrocarbons indeep and ultra-deepwaters, the SCM system faces important environmental,safety and reliability challenges and little research has been done in this area.Analysis of the SCM reliability then becomes very fundamental due to the hugecost associated with failure. Several tools are available for this analysis, but theFMECA stands out due to its ability to not only provide failure data, but alsoshowcase the system’s failure modes and mechanisms associated with thesubsystems and components being evaluated. However, the technique hasbeen heavily challenged in various literatures for several reasons. To close thisgap, a novel multi-criteria approach is developed for the analysis and ranking ofthe SCM failures modes.This research specifically focusses on subsea tree-mounted electro-hydraulic(E-H) SCM responsible for the underwater control of oil and gas production. Arisk identification of the subsea control module is conducted using industryexperts. This is followed by a comprehensive component based FMECAanalysis of the SCM conducted with the conventional RPN technique, whichreveals the most critical failure modes for the SCM. A novel framework isdeveloped using multi-criteria fuzzy TOPSIS methodology and applied to themost critical failure modes obtained from the FMECA evaluation usingunconventional parameters. Finally, a validation of these results is performedusing a stochastic input evaluation and SCM failure data obtained from theoffshore industry standard reliability database, OREDA.