Quantitative Risk Assessment as a Design Tool—Recent FPSO Experience

Abstract

Summary Quantitative risk assessment was used as a tool for the conceptual and detailed design of two floating production, storage, and off-loading (FPSO) installations. Results from the risk-assessment study were used to identify significant risk contributors that influence the design and operation of the facilities and to demonstrate that the risk-acceptance criteria adopted by the company were met. The results were also used to identify opportunities to further reduce the risk to a level that is as low as reasonably practical (ALARP). Traditional risk, reliability, and consequence analysis methods were used to evaluate impacts from process and marine facilities and to determine the design of accidental loads during the conceptual engineering and design phases. Results were used as data for a detailed fault-tree analysis of accident scenarios and used to set the design criteria for significant structures and facilities. In addition, analyses of subsea facility interfaces and field operations were performed to incorporate the full development scope. Particular attention was given to subsea pipelines and flexible risers as well as tanker operations and their effects on FPSO operation and design. Event frequencies were determined from industry data and conditioned for the special design and operating features of the chosen FPSO concept. Risk sources, impacting fatal accidents, impairment of safety functions, and loss of asset value, were quantified for use in demonstrating an acceptable level of risk and to test opportunities to further reduce operating risks. Results from the analyses show that process fires and explosions dominate the risks to personnel and safety functions, followed by cargo tank explosions. Tanker collisions, subsea pipeline and riser leaks, and turret operations were found to represent significant asset risks. Design development and operations planning efforts focused on these areas to reduce risk and improve reliability.