Study On Predrilling Engineering Design Method For Top Tension Riser System Of Tension Leg Platforms

As the science and technology advanced,energy demand increased,the offshore oil exploration and exploitation has become more and more important.For oil exploration and exploitation,the tension leg platform(TLP),a main type of platform,has the characteristics of cluster wells development,dry tree,SBOP,great sTab.ility and well heave performance.Since it largely decreases operation difficulty and increases the operation effectiveness,it gets more attention.In China,the study of TLP is basically in the blank stage and the predrilling design method for cluster riser system is still on primary stage,but cluster riser system security play crucial role in drilling and production operation.The study,sponsored by CNOOC project “Technology research on the drilling and completion of top tension riser of Tension Leg Platform”,on predrilling design method for top tension riser(TTR)system of TLP was carried on which provides technical support for the application and operational safety of TLP.1.The study on top tension riser system configuration for tension leg platformThe structure and size of TTR affect operational safety.Analysis on the application conditions of single and double TTR,then based on the criterion of riser equivalent stress and collapse and propagation collapse and burst in API RP 2D,the design method of wall thickness and diameter for TTR and TTR selection process are esTab.lished,which is carried out to guide TTR selection.According to the configuration of PTTR and DTTR system,the composition of TTR system configuration is analyzed before TTR system configuration process es Tab.lished.2.The study on tension calculation method of top tension riserTLP is sensitive to variable load.Cluster riser structure causes the presence of wake effect which causes riser collision and premature destruction.On the basis of collision analysis of cluster rise,study on the TTR tension calculation method.To avoid collision and reduce variable load of TLP,optimization scheme and method and process are proposed.By comparing the riser spacing of the before-and-after optimization,the feasibility of optimization scheme is proved.3.The study on design method of wellhead layout and spacingThe design of seabed wellhead layout for TLP has close relation with the safety of TTR.Both too small wellhead spacing and large inclination angle of the TTR will result in riser collision.Once the collision took place and installation was not smooth,the performance of the TTR will reduce,which will cause operational risks.With the all operation process considered,seabed wellhead layout design criterion is esTab.lished.Based on seabed wellhead layout design requirements and collision analysis,wellhead layout design method and process is proposed.Finally seabed wellhead layout is determined.4.The study on Vortex-induced inhibition scheme of top tension riserThe VIV is one of the main factors leading to the devastation of TTR.Study on VIV mechanism and inhibition mechanism of Vortex-induced suppression device,analysis on the fatigue damage of riser system,then different quantity of Vortex-induced suppression devices are drafted.By analyzing different Vortex-induced suppression schemes in SHEAR7,the optimal one is determined.