Availability Assessment of Electrically-Operated Blowout Preventers

Abstract

Offshore drilling industry is confronted with safety and environmental challenges imposed by the risk of oil and gas blowout accidents. The blowout preventer (BOP) has been an important safety-critical system for preventing blowouts during drilling activities. BOP failures and associated rig downtime, on the other hand, have resulted in significant revenue loss. The industry therefore has put emphasis on improving the availability and safety of the BOP. Currently used BOPs comprise of both electrical and hydraulic systems, while a new design concept, the electrically-operated BOP seems to be a candidate to overcome some of the availability and safety problems of using hydraulic. Electrical Subsea & Drilling AS has developed a new design concept technology for the electrically-operated BOPs. This engineering project is currently in the proto-typing phase, and in the future it is necessary to verify the reliability performance of the new BOP as a commercially viable solution. This report suggests a quantitative reliability modelling as an approach to compare the two BOP design principles. The selected method is reliability block diagram (RBD) driven Petri nets (PN). PN can be plugged into the RBD so that it can model some of the component. In the case study, annular preventer and pipe ram preventer are modelled with PN to reflect the effect of proof testing, partial testing, and repair. For BSR, PN is used to see how if two redundant BSR can improve SIL level. PN is both graphical and mathematical tool. It is therefore easy to understand for those who are not familiar with reliability analysis. The model therefore is expected to be serve as a visual presentation of BOP availability analysis to facilitate communication with system designers or engineers, for example. The suggested model is flexible due to the inherent characteristic of Petri nets, and it can therefore be elaborated if there is a need in the future.