Dynamic Bayesian network-based reliability and safety assessment of the subsea Christmas tree

The major functions of the subsea Christmas tree include production management, wellhead pressure control, chemical reagent injection, and oil/gas production safety control. It is necessary to investigate the reliability and safety of the tree for safe and stable operation of subsea production systems. A fault tree and a dynamic Bayesian model are used to assess reliability and safety and to consider the time slice based characteristics of the reliability. Using the control variable method, impact analysis is performed to quantify the impact of each failure rate on the system and sort the impacts of failure modes on reliability and safety. Finally, failure prediction is performed. The results show that the annulus loop has the lowest reliability and is the most likely to fail. The failure rate of the tubing hanger has the biggest impact on system reliability, while the failure rate of the choke valve has the biggest impact on system safety. When the tree fails, the failure probabilities of the tubing hanger and the valve group of the production loop are relatively high. On the basis of the above results, corresponding control measures are proposed that can significantly reduce the failure risk of the tree. (C) 2020 Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

Automated summary

The subsea Christmas tree plays a crucial role in production management and safety control, with the annulus loop identified as the least reliable component. The tubing hanger has the greatest impact on system reliability, while the choke valve has the biggest impact on system safety. Proposed control measures aim to significantly reduce the failure risk of the tree.