Study On The Three-dimensional Motion Compensation System Of Ultra-deep Drilling In Deep Water

Drilling platform is an essential facility of oil production and scientific drilling in offshore, it has the movement of six degrees of freedom which caused by water, winder and other factors. Experience of the offshore drilling operations has shown that no matter how the level of performance of rig was, to ensure the stability of weight on bit (WOB) and improve the efficiency of deep-sea drilling, it must be equipped with the motion compensator when drilling in the sea.Currently, the motion compensation system of drill string is designed for the movement of drilling platform. When drilling in shallow water, the movement of platform is the main reason which caused the fluctuations of WOB, so the WOB will be stable and the efficiency of drilling will be improved by eliminating the impact of movement of platform, and improve the efficiency of offshore drilling. However, the role of water has on the WOB can not be ignored under the deep-sea drilling conditions, it will be significantly reduced the compensation accuracy of WOB. Therefore, it is necessary to take a appropriate compensation control scheme to improve the precision of compensation.For the characteristics of deep-sea drilling, three-dimensional motion compensation system of drill string is put forward in this study, which will guarantee the stability of WOB in the drilling operating environment of deep-sea. To verify the feasibility of compensation and reliability of control strategies, it is essential that take on the research of simulation and experiment, which will provide theoretical and practical basis for the development of motion compensation system of drill string.The overall goal is to build a semi-physical simulation system of motion compensation of drill string based on theoretical analysis in this thesis, through the design of compensation scheme and parameters, nonlinear analysis of drill string, mathematical modeling of compensation system, the design of controller, the simulation and experimental studies of compensation system, the WOB compensation system is taken by the theory and experiment, it is proved that that compensation program is feasible and the results are reasonable. According to the research process above, the main contents of this paper is divided into six chapters, the specific focus of each chapter is as follows:ChapterⅠreviews the development process of drill string motion compensation system, research and its inadequacies, analysis of the inadequacies of current motion compensation system in deep-sea, and then the content of this study is proposed.ChapterⅡdiscusses the most basic part of drill string motion compensation system, the design of compensation program of drill string and its parameters. for the characteristics and requirements of deep-sea drilling operation and pressure compensation. The indicators of drill string motion compensation system of deep-sea, the appropriate compensation programs are put forward; the parameters of drill string compensation system according to the sea conditions with the specific work are determined:Finally. the relevant parameters of compensation program is established.ChapterⅢanalyzes the effect of water has on the drill string in deep-sea, which provides the reference of the design of compensation system. Through the necessary assumptions and simplifications of compensation system, the nonlinear analysis of drill string is taken on by the use of the finite element method.ChapterⅣdiscusses how to set up the mathematical model of motion compensation systems. Firstly, the mathematical model of the 4/3-way proportional valve controlled hydraulic cylinder is established, and then the mathematical model of accumulator and hydraulic cylinder is put forward, on the basis of the active and passive compensation system. the mathematical model of semi-active compensation system is put forward.ChapterⅤfocuses on the design of controller of compensation system and the simulation of system, the composite control strategy of flow compensation and adaptive control is taken to improve control accuracy.ChapterⅥachieves the experiments of the compensation system for semi-physical simulation. By the use of Simulink/xPC control system and the adaptive control strategy, the semi-physical simulation model of compensation system is established.Finally, it is the summary of the paper, which gives the conclusions, innovations and vision for the future.