Structural Design And Research On Control Strategy Of Flexible Hang-off Device For Drilling Riser

The riser is an important unit in the exploration and development of deep-water oil and gas in the ocean.In order to improve the safety of the riser when the platform deal with the typhoon and other severe conditions,Hard and soft hang-off configurations of riser are studied which are used when the platform avoid typhoon.The flexible riser hang-off device is designed based on the existing research work to compensate the deep movement.The structure of the flexible hang-off device for drilling riser and each module were designed in this thesis.The working principle of three modules of the flexible hang-off device for riser were explained.The structural dimensions of each component of the three modules were designed and calculated.Finally,a 3D model was built in 3D modeling software Solid works.For non-standard parts with irregular shapes,the 3D models were imported into the finite element analysis software ANSYS Workbench for finite element analysis,and the part structure is modified according to the analysis results until the required part structure were obtained.The hydraulic system of hang-off device were designed on the basis of the structure of motion compensation mechanism of flexible hang-off device for drilling riser.The common accumulator scheme and the one-way differential hydraulic cylinder scheme were designed,and their feasibility,advantages and disadvantages were analyzed.Three dynamic load compensation control strategies for drilling riser are proposed,and their feasibility,compensation capability and power consumption are analyzed.Finally,a back pressure variable damping control strategy with good compensation performance and simple hydraulic system structure was selected.Finally,the model of the Flexible hang-off device for drilling riser was established in Simulink.The riser heave motion were compensated by acceleration control for riser and displacement control for piston.The parameters of each module were adjusted,and the parameters of the PID controller were adjusted by trial method.The hydraulic system and control strategy were simulated and analyzed.By adjusting the parameters of accumulator,proportional throttle valve,riser load and other modules,the law of its influence on compensation performance was studied and its internal reasons are analyzed,which can be used as reference for parameter setting of flexible hang-off device.