Risk Assessment Of Subsea X-Tree And Analysis Software Development

As an important equipment of the subsea production systems,the subsea X-tree needs to ensure the ability of long-term operating safety during underwater working,for which the structure of the subsea X-tree has to be secured and reliable.Since the long-term working in a complex and harsh environment,the subsea X-tree will be affected by ocean current,falling objects,fishing net towing or other external loads that might cause structural damage which will bring immeasurable environmental pollution and economic losses.Therefore,it is essential to launching a risk assessment toward the subsea X-tree structure.To achieve that goal,this dissertation is meant to solve the problems initiated by complex invalid mode and low accuracy of dependable evaluation model of subsea X-tree structure,appraises the risk of subsea X-tree structure and relatively develops the software for it.The mainly works are as followed:By investigating the subsea X-tree structure,the composition of it could be defined and as so its third-party load constitution could be analyzed.Failure Mode,Effects and Critically Analysis(FMECA)and Fault Tree Analysis(FTA)were employed together to analyze the risk of the structure of subsea X-tree eventually after comparing and dissecting all of existing analysis methods.The ABAQUS / AQUA module is used to analyze the stress and deformation of the subsea X-tree—Jumper model under the action of different directions of ocean current force,and the failure mode of the subsea X-tree structure under the action of ocean current load is defined,which provides some guidance for the layout and installation of the subsea X-tree.Taking falling pipeline and dropping anchor as examples,the impact of collision on the structure of subsea X-tree is analyzed by using ABAQUS / Explicit,and the failure mode of subsea X-tree structure under collision load is clarified,which provides a theoretical basis for the safe operation of subsea X-tree.Based on the configuration analysis and external load analysis of subsea X-tree structure,the FMECA model of subsea X-tree structure is established,and the main failure modes,failure causes and failure effects of subsea X-tree structure are defined.A FTA model with the top event of “structural failure of subsea X-tree” is established,and the failure rate of the bottom event of the fault tree is determined by fuzzy comprehensive evaluation method.Through quantitative analysis of the FTA model,the failure rate,reliability,life curve and key importance of the top event “structural failure of subsea X-tree” are obtained,and the influence of structural failure of subsea X-tree is clarified The most effective failure mode.Based on the risk assessment model of subsea X-tree structure established in this paper,the fault tree analysis software of subsea X-tree structure is developed by using C# language,so as to realize the calculation of structural reliability index and life prediction of subsea X-tree.