Risk-based Approach for Fatigue Integrity Assessment of Offshore Piping in the Arctic Environment

摘要

Hydrocarbon release (HCR) from offshore piping has beenidentified by the international standards and regulatoryauthorities as a potential hazard for safe oil and gas productionin the Arctic region. Due to the requirement for higher-strengthsteel pipes (meaning thin-walled piping, which is more prone tovibrations) in the Arctic region, it seems quite likely thatvibration induced fatigue (VIF) failure of topside piping willform the lion’s share of HCR on offshore oil and gas (OOG)platforms in the Arctic region. Furthermore, due to the “zero oilspill” requirement in the Arctic region, VIF failure of processpiping is undesirable and thus must be prevented by maintainingthe appropriate fatigue integrity of the pipework. In this regard,the authors have presented a risk-based approach for the fatigueintegrity assessment of offshore piping on OOG platforms in theArctic environment. Fuzzy logic is used to determine the risk offatigue failure posed by topside piping. The value of riskcalculated depends upon the IF-THEN rule base (formulatedusing expert knowledge) and the shape of membership functions(MFs) chosen for risk, likelihood of failure (LoF) andconsequence of failure (CoF). The value of LoF in turn dependsupon the value, MFs and rule base of the measured vibrationalvelocity (VV) and the probabilistically estimated remnantfatigue life (RFL) of topside piping. The outcome of the fatigueintegrity assessment using the proposed approach is thecategorization of piping into high-, medium- or low-riskgroupings. Piping in the high-risk category is thereby prioritizedfor inspection, thus preventing HCR in the fragile Arctic region.An illustrative case study, demonstrating the usability of theproposed approach, is presented.