Preliminary Design And Analysis Of Top Tensioned Riser For A New Type Of Deep-draft Dry-tree Semi-submersible

Petrochemical products are the basic material for the development ofindustry. As a large number of oil explored on land, people begin to shifttheir attention to ocean. In order to exploit offshore oil and gas, peoplehave developed a variety of marine structures. Currently, oceanengineering is shifting to deep water area, which raises a lot of newchallenges to marine structure design and analysis.As a system linking the floating structure to subsea well, riser systemis indispensable for ocean engineering. Despite its importance, riser is oneof the weakest parts of the system. Of all types of riser, Top TensionedRiser (TTR) is widely used for the facts that it can be used for drilling,completion, workover, as well as injection and production. The assignmentof this thesis is to carry out the preliminary design and analysis of TTR.(1) Analysis the deep-draft dry-tree semi-submersible by software Aquaand Orcaflex. Conduct analysis in both frequency domain and timedomain. Coupled analysis of semi, mooring system and riser underdifferent sea condition is conducted to get the time history data of themotion of semi. The data will be used in the analysis process of riser.(2) Analysis the influence of top tension factor (TTF) and stiffness of thetensioner on the behavior of riser. The result shows that TTF has agreat impact on the behavior of riser, while the stiffness of thetensioner influences the vertical motion of riser.(3) Study the layout of TTR on seabed by programming in Matlab. As an efficient algorithm, the Evolution Strategy is adopted. Result producedby the program is verified by result from software Lingo. But theprogram works more efficiently. A method of―Grouping‖is raised todeal with the problem that when there are many risers, the programneeds much time to get the result. This method is proved to beeffective.(4) Design the riser system for the new type of platform using softwareOrcaflex. The designation is based on API RP2RD. The response ofthe riser under different sea states are checked, as well as the strengthof the structure. The fatigue life of the riser is calculated to make surethat the riser wouldn’t fail. The interference between risers is alsoanalyzed.