Analysis of safety and impact probability of subsea Christmas tree impacted by falling objects.

At present, there is no clear data to analyze the probability and impact of falling objects on the subsea Christmas tree. However, during the long-term operation in the complex deep-sea environment, objects may fall and hit the tree due to the anchored platform, fishing boat operation or other reasons, the impact of large heavy objects onto the tree can potentially give rise to the development of internal forces higher than those for which the tree was designed to. Therefore, aiming at the risk problem of falling objects, the paper presents the development process and results of an improved impact probability numerical method. And the safety model of falling object impact on the tree is established. Preliminary results indicate that the method offers valuable insight including and beyond a probability estimation of third-party damage, and the safety results were obtained. At the same time, the influencing factors of the tree impacted by falling objects are analyzed, and the serious influencing factors are obtained, which provides theoretical basis for the design and optimization of the protection frame of subsea square equipment. • The applicability of numerical calculation for falling objects impact is enhanced. • Impact probability of the tree is generally in the order of 10−9. • Impact probability increases first and then decreases at the turning point 50 m water depth. • Protection frame structure can be simplified when water depth exceeds 300 m [ABSTRACT FROM AUTHOR]