Dynamic Analysis Of Installation Of The Subsea Tree

The subsea production system is widely used in deepwater oil and gas development.With the increasing of water depth,lowering difficulty,risk and costs are greatly increased.At present,the domestic can not complete the installation independently,so it is important to carry out the research on the installation of the subsea production system to improve the national oil and gas safety strategy and promote the development of offshore oil and gas development.The installation of subsea tree which is one of the main equipment of subsea production system is the research object in this thesis.Various deepwater installation methods are introduced.The advantages and disadvantages of each deepwater installation methods are compared based on the SWOT analysis.Then the adaptability comparison has been conducted.Secondly,wire rope installation and fiber rope installation have been compared.The performances of the lines have been analysed and compared.It is found that the fiber rope is suitable for deepwater installation,and wire rope in deepwater installation is less applicable.Static analysis and dynamic analysis are carried out of the two different installation methods.In static analysis,horizontal offset cased by current and stretched length of lines are compared.In dynamics analysis,the lengths of lifting line causing resonant motion are determined.It is found that the resonance occured in shallow water when using fiber rope and the resonance occurred in deeper water when using wire rope.And when lowring heavy equipments,the resonance is more prone to occur.Accepted criteria which have to be satisfied in installation process are confirmed according to DNV rules.The results of dynamic analysis are compared with the accepted criteria,and the critical sea conditions of subses tree installation are obtained.In the end,subsea tree lifting through wave zone is studied.A simplified algorithm of the structures lifting through wave based on the DNV rules has been proposed,and accepted criteria which have to be satisfied are raised.The division and analysis of load cases during subsea tree loweing through water surface have been completed.Slack sling and DAF are calculated respectively,and the critical sea conditions of subses tree lifting through wave zone are obtained.The simulation of subses tree lifting through wave zone has been conducted based on FLUENT dynamic mesh local reconstruction method,the air volume fraction and dynamic pressure distribution are studied.