Numerical Simulation Research Of The Collision Of Top Tensioned Risers In Tension Leg Platform

Global oil and gas industry is moving into the ocean,the marine oil and gas resources have become the focus of contention from today to the future.The production platforms and risers have been developed rapidly.The safety of tension leg platform is more higher than others from the view of platform put into production.The tension leg platform(TLP)is mostly dry tree platform,and usually corresponds to top tensioned riser.The offshore floating platform and underwater production system is connected by risers.Compared with the shallow water riser,deepwater riser is in a more complex environment and has become the key part of the whole deepwater oil and gas development equipment,and it is also one of vulnerable parts in the whole system.Combined with the motion of floating bodies、environmental loads and internal flow,adjacent risers closely arranged causes the collision due to different dynamic response,a larger impact stress is generated,the safety operation of risers is affected.In this paper,the research progress of riser collision problems is stated in detail.The environment loads、functional loads and the offset of upper floating body which acted on the risers during operation period is analysed.The main reasons which caused impact between adjacent risers is summed up,such as the shielding effect 、 the wake indeced oscillations(WIO)and the vortex induced vibration(VIV).The global impact analysis is simulated by OrcaFlex under the 100-year sea conditions,the risers is divided into several parts and Cd of every part is solved.Sensitive parameters of TTR intervals、the offset of upper floating body、wake model and the drag coefficient is considered in global impact analysis,the position、velocity、stress of collision is acquired.Based on analyse of global impact,moment and relative velocity at the moment of collision is extracted,the local impact is simulated by ABAQUS.The influence of impact velocity、internal pressure、friction factor 、 angles on the collision are paralleled from considering the riser-water coupling effect or not.Appropriate measures should be taken to increase the safety measures,such as the reasonable arrangement of riser spacing,and safety measures in the area where the collision is easy to occur,so as to avoid the contact or collision between adjacent risers.