The Influence Of Buoy On The Configuration Of Flexible Riser

In order to meet national economic growth and strategic needs,the development of offshore oil and gas fields will gradually move towards the deep sea.With the development of deep-sea oil and gas fields,flexible risers used to connect floating bodies on the sea surface and underwater facilities have also been widely used.However,as the water depth increases,the tension of the flexible riser at the suspension point will increase,greatly shortening the service life of the flexible riser.For this reason,in engineering applications,unequal numbers of buoys are often added to the flexible riser to produce a gentle waveform configuration of the flexible riser,so as to reduce the tension of the suspension point of the flexible riser and reduce the possibility of the sloshing of the upper floating body spread downward,Thereby increasing the service life of the flexible riser.Therefore,it is of great significance to the design of flexible riser engineering to conduct research on the influence of buoys on the configuration of flexible riser.The thesis focuses on the influence of buoys on the configuration of flexible risers,and conducts the following research from two aspects: theoretical modeling and finite element numerical analysis:(1)Establish equivalent mechanical model of buoy and flexible riser.The buoy on the buoyancy section of the slow waveform flexible riser is equivalent to a pipe section with a uniform diameter,and the effective wet weight of the flexible riser per unit length in water after equivalent is obtained;the configuration of the slow waveform is divided into the suspension section,Three sections of buoyancy section and descending section and carry out force analysis of micro-element section respectively,based on the theory of large deformation beam,considering the effect of fluid and current in the pipe,the control equations and boundary conditions of flexible riser under gentle waveform layout are obtained,MATLAB is used to obtain the configuration and tension distribution of slow-wave riser in ocean current and internal flow.(2)Research on the configuration of flexible riser by pontoon.The simplified model of flexible riser was established by Orca Flex,and the configuration changes of the riser under the action of ocean current and internal flow were simulated and analyzed.The results of simulation analysis were compared with the results of theoretical analysis.The results obtained by the two methods were basically the same.Prove the correctness of the analysis process.Using the simplified finite element model established by Orca Flex,the influence of the buoy distribution on the configuration of the slow-wave riser was studied,and the density,spacing,height,position of the buoy and the length of the buoyancy section and the total length of the flexible riser,the internal fluid of the pipe were calculated The density of the flexible riser configuration,effective tension and bending moment changes.(3)Research on the configuration of flexible risers with double waveAiming at the problems that the lazy wave flexible riser has steep wave and high buoyancy section tension,and the movement of the upper floating body is very sensitive to the change of fluid density in the pipe,a dual-wave riser study was carried out.Orca Flex was used to study the dual-wave riser in reducing the tension of the buoyancy section of the lazy wave flexible riser and the steep wave.The influence of the spacing between the buoyancy sections and the length of the buoyancy sections on the configuration and effective tension of the flexible riser is calculated.