The Research Of Pipe Racker System For Offshore Drilling Platform

With the continental petroleum resources drying up,the exploitation of offshore oil resources is increasingly attracting the attention all over the world.Meanwhile,the technology and equipments that are related to offshore drilling also get a chance to develop continuously.Offshore drilling platform is a fundamental tool for offshore oil and gas exploitation,and the system of pipe racker is the core subsystem of the pipe handling system on the offshore drilling platform,which plays an important role.The European and American countries have mature technology and industrial products in the research of pipe rackers,whereas our country mainly depends on imports,as has an obvious gap against occident in tterms of theoretical research and engineering application.This dissertation is aimed at the system of pipe racker that domestic offshore engineering equipment urgently needs.Deep study on pipe racker of the offshore platform is of great value to filling the domestic blank,breaking the monopoly and improving the engineering of pipe racker system.Based on a scientific research project processed by CNPC,the pipe racker system studied in this dissertation can meet the requirement of operation depth from 91 m to 122m(300-400ft)of mainstream jackup drilling platforms and part of semi-submersible drilling platforms.The main contents are as follows:Firstly,it is an overview of the offshore drilling platform pipe handling system's composition and function.The major role of pipe racker in the process of drilling pipe handling is to combine drill pipes into a drill-pipe stand,place the dill-pipe stand to the specified location in the second floor of fingerbord and grab the drill-pipe stand from fingerbord to help the top drive to drill.In the process of drilling,we should disconnect the drill string to drill pipes and move them to the pipe stack area.Compared with foreign countries,the domestic study of pipe racker for offshore drilling platform only focuses on a few large deepwater drilling platforms,and remains in a single device level considering study of the control system,which makes it unable to implementthe real automatic pipe handling requirements.Therefore,this paper is of great value to perform the design,simulation and experimental research.Sencondly,according to the operation environment and job requirements of offshore drilling platforms,consulting some relevant international offshore engineering equipment design experience,this paper determines the optimal process for the process of pipe handling and put forward the structure of pipe racker and function requirements of the parts.By using the method of vector closed graph,we establish the kinematic model of the grapper of the pipe racker and make the relationship between the movements clear.The dissertation makes use of simulations to get the main curves of the institutions,so as to achieve the moving relationship between the gripper linkages.Choosing the means of equivalent mechanical model,regarding the mechanical lingage as equivalent object,dynamically modeling the gripper,the dissertation gets the dynamic characteristic of the gripper by using the simulation and then analyze them.Thirdly,since the pipe racker works in an offshore environment,the strong fluid-structure interaction phenomenon widely exists in the process where offshore winds interact with the pipe racker.In order to study the loads on the structure,and velocity vector,pressure and vortex distribution in the flow field,the dissertation builds a simplified model of fluid-structure interaction between the pipe racker structures and the flow by recovering the Navier-Stokes equations using the lattice Boltzmann method based on the theory of fluid-structure coupling.In addition,the corresponding calculating program is developed.Based on that,the smargorinsky model of large eddy simulation is used to model the process.Taking the wind load of working pipe into consideration,the distribution of stress on key parts of the pipe racker is analyzed,and the stress analysis diagram is figured out.Combined with the structure's load and the vortex shedding rule,the model analysis of the independent pipe and the pipe racker together with the pipe is implemented using the Abaqus software.The results show that the pipe racker together with the pipe is a low frequency structure,and its natural frequency is lower than that of the isolated pipe.And its vibration response is mainly controlled by a number of lower order vibration modes.The critical wind speed exciting the lower order vibration response of the system is small,so strong vibration of the system can not be caused.All of the above prove that the structure design of the pipe racker can meet its operational requirements.Fourthly,onsidering pipe racker actuator as the research object,we completed the hydraulic system design,established key element mathematical models and analyzed parameters that affect the performance of the system theoretically.Through AMESim software simulation method,we researched the stability of the main arm drop and the synchronicity of walking motion and established the corresponding AMESim simulation model.The dissertation firstly compares the results from simulations and analyzes the influence on the stable of main arm's descending caused by different forms of counterbalance valve.Then the movement results of synchronized travelling motion is studied,the dissertation discovers that the upper and lower part of the pipe racker's synchronized travelling motion is inconsistent,which will cause a large vibration to the hydraulic system while working thus may also cause a great vibration to the mechanical system.A solution is proposed and implemented to solve and optimize the problem.Fifthly,in view of the offshore drilling platform pipe racker's characteristics,such as numerous joint,limited working space,and requiring to be used with multiple devices,we design control method,automatic operation method and control process of pipe racker,and verify them through simulation trial on the visual simulation platform.At the same time,pipe racker control requires high precision,while many joints need to move synchronously to complete the corresponding working procedure,and the pipe racker has to hold the pipe,which can be as long as nearly 28 meters,requiring a strict limit the system overshoot and oscillation.While the traditional PID control technology is difficult to achieve the task,this paper adopts the fuzzy self-tunning PID control algorithm to solve the problem of high precision motion control and synchronization movement joints without overshoot.The fuzzy self-tunning PID control algorithm not only maintains some advantages of the fuzzy control algorithm,such as flexible and fast control and not relying on the accurate model,but also inherits the advantage of high precision of the traditional PID control algorithm,achieving the intelligent control of the system.Through simulation with Matlab and comparison,we get the conclusion that fuzzy self-tunning PID control algorithm is far better than the traditional PID control algorithm considering the amount of overshoot,response speed and resistance to disturbance.Furthermore,the fuzzy self-tunning PID algorithm has a low operation requirement,making it very suitable for running on PLC system.