A Comprehensive Risk Assessment Model for Blowouts on Drill Ships: An Extended FMEA Integrated with IVN-Fuzzy SWARA&EDAS.

Offshore drilling operations present challenges, including operational difficulties, human factors, and environmental conditions. Loss of well-control poses significant risks to crew safety, the marine environment, and the economy. To prevent these accidents, it is crucial to systematically prioritise blowout-related failure types under uncertainty. This paper indicates an extended risk assessment framework for blowout accidents on offshore drilling vessels. The proposed approach integrates extended Failure Modes and Effects Analysis (FMEA) with Interval-Valued Neutrosophic fuzzy SWARA and EDAS methods. In addition to the classical FMEA, the parameters Maintainability and Cost were included in the evaluation. FMEA systematically identified failure modes, while the IVN fuzzy structure was used to model uncertainty in expert assessments. The relative importance of risk parameters was determined using the SWARA method, and error types were prioritised using the EDAS method, consistent with the obtained weights. The study was conducted using a generic drill ship case study focusing on well-control-related blowout risks. The results indicate that blowout risk is predominantly driven by failure modes associated with primary well-control systems and inadequate human intervention. In contrast, environmental conditions and isolated positioning disturbances play a secondary role. The findings provide a decision support tool for systematically assessing blowout risk under uncertainty.