Research Of DP System Of Deepwater Semi-submersible Drilling Platform

As the development of shipbuilding industry and oil exploration in China, traditional station-keeping system for ship and ocean engineering could not meet new requirements of platform's normal operation in deepwater, has brought about the great development in the area of Dynamic Positioning(DP) technology. DP system in deepwater has been used in many offshore platform operations, while each of these operations benefits from a DP system's ability. Therefore, the research and analysis of DP system contributes guiding and realistic significance to development of offshore engineering.This thesis focuses on the research of environmental load and theoretical analysis of DP system, and taking a deepwater semi-submersible drilling platform (Semi) as an example. At first, a simple analysis of basic requirement of Semi's DP system design is presented, and the DP thruster system for Semi which gives out the configuration of thrusters is introduced. All the above work is for the sake of carrying out farther work, such as DP model establishment and numerical simulation. In order to acquire accurate information of environmental loads which are used to analyze DP system for Semi, the external loads on the platform due to wind, current and wave are calculated in theory, the wave drift force is mainly discussed. The results from numerical calculation are analyzed and evaluated to provide calculation techniques of environmental loads suitable for Semi. According to the methods which some classification societies recommended, a program has been developed to calculate the DP capability polar plots of the platform under design condition. The DP capability analysis includes intact mode and all failure modes of DP system to verify the security and reliability of the DP system. Furthermore, a numerical model of the whole DP system with PID controller, Kalman filter and thrust allocation algorithms is established, and.a corresponding dynamic analysis program for DP system has been developed. Time-domain and dynamic simulations are carried out by this program which is referred to analyze the performance of the platform with DP system under design conditions. Finally the results of simulations proved that the DP system works well, and has a good security and economic performance.By this research, we will almost master the basic design means of DP system of deepwater Semi. All these work are possessed of valuable reference to practical engineering application, and have a good preparation to develop our own DP analysis system as well.