Research On Dynamic Analysis And Compensation Strategy Of Riser Flexible Suspension Device

As an important equipment for semi-submersible drilling platforms commonly used in deep sea drilling,a riser connects the drilling platform and the seafloor wellhead,forming a channel that is isolated from the seawater for the entry of drilling tools and return mud.When the platform encounters extreme weather disasters such as typhoons,it is necessary to stop the drilling work and perform the avoidance operation.At this point,the platform first recovers all drill tools,and then disconnects the riser from the bottom riser assembly and the blowout preventer,recovers some of the risers,and then suspends the remaining risers together with the platform to withdraw from the typhoon area.At present,the commonly used riser suspension methods are hard suspension and soft suspension.The main difference is that the boundary conditions at the top of the riser are different.The two suspension methods have their own advantages and disadvantages,and are applicable to different working conditions.Aiming at the current need for safe suspension risers when the current semi-submersible drilling platform is performing a stage-avoidance operation,a new riser suspension scheme is proposed,named a riser flexible suspension device,and a corresponding compensation strategy is designed for simulation analysis.The device should be easy to install and use,and significantly improve the safety of the riser suspension.By collating the existing data on the suspending method of the riser and the equipment,the development situation of the riser suspension at home and abroad was understood,and the working principle and characteristics of the riser were analyzed.Combined with the requirement of the suspending device for the riser,the system design plan for the riser suspension system was formed.After the mechanical analysis of the suspension system,the flexible suspension system must use a compensation control system to ensure that it achieves compensation of the riser acceleration within a limited range of travel.Because the working condition of the flexible suspension system is to use small displacement to compensate for the acceleration caused by large displacements,this paper designs,calculates and theoretically analyzes the compensation strategy of the flexible suspension system,and in turn forms a proportional compensation method,advanced compensation method and pressure limiting valve control.The compensation method uses three compensation strategies,and studies the principle complexity and control compensation capabilities of different compensation strategies.Then select the easy-to-implement proportional compensation method and pressure-limiting valve control compensation method to perform dynamic analysis to determine the physical equipment requirements for different compensation strategies.Finally,the most feasible pressure-limiting valve control compensation method was selected to design the hydraulic system for simulation modeling and analysis.The deviation between the calculation work parameters of the pressurelimiting valve control compensation method and the compensation effect and the simulation results was verified,and the simulation model was gradually improved.Future research will lay the foundation for further research.