Barrier Analysis of Emergency Disconnect on DP Mobile Offshore Drilling Units

Technical, operational and organization barrier elements related to the emergency disconnect on dynamically positioned mobile offshore drilling units on the Norwegian Continental Shelf are identified. Position loss scenarios are analyzed based on the published station-keeping incidents by IMCA (International Marine Contractors Association). How these barrier elements may fail in different types of position loss scenarios are addressed qualitatively and quantitatively in an event tree model. A case study is provided in the paper and notational probability of failure to disconnect given position loss is calculated. Risk reduction effect of various barrier elements are investigated by sensitivity studies. The paper provides insights into risk given position loss and failure of emergency disconnect on DP MODUs. It offers decision support for risk management of DP drilling and well operations in shallow water and harsh environment.