The Study On Raising And Lowering Motion For Offshore Platform Based On Hardware-in-the-Loop Simulation

Offshore platform is one of the most necessary equipments for oil extraction in the ocean. Many series of platforms have been developed in recent years, such as gravity platform, jacket platform, self-elevation platform and tension leg platform, etc., to meet different geologic and marine conditions. As the increase of the world oil demand and decrease of the large oil field reserves , people have to give their attentions to the thousands of small oil fields whose geologic conditions are generally bad. The extraction method and equipments needed in these kinds of oil fields are distinctive from those in normal oil field. Most basic requirements are that the platform can be used repeatedly, has the ability to store oil and has simple structure.For the need of extracting more marginal oil fields, a new-style platform has been developed, which is called bucket foundation offshore platform. This kind of platform has the pull-out and suction capability based on principle of suction pile. Much research work on bucket foundation mechanism has been done recently. As the recognition and use of this kind of platform, a question must be emphasized, that is how to make platform lower from marine surface to bed and raise from marine bed to surface. The raising and lowering procedures should be considered because of the platform's mobility. Traditional method is to depend on floating crane, On one hand, which increases the installation expenses, so that the total benefits of the oil exploitation decrease, on the other hand, which can not be carried out in shallow sea because of no way to offer enough sea gauge. In order to resolve this difficult problem, a new feasible method for the raising and lowering procedures of the platform is presented in this dissertation. This method is called pumping-out-and-pumping-in method which means that self-raising or self-lowering of the platform is implemented by pumping water into the cavity or pumping water out of the cavity. The cavity is the bucket columns and/or sealed bucket foundations. That is to say, die raising or lowering procedure of the platform is controlled by regulating the total flow pumped in or pumped out of the cavity, and the platform stability is controlled by regulating every cavity flow.In fact, the platform is very large. If the test is performed in field, the cost must be high, and the test period is also very long, at the same time, there is danger in the test. In order to testify the feasibility of the method, hardware-in-the-loop simulation is used for analyzing the raising and lowering procedures of the platform in this dissertation. To validate the reliabilityof the hardware-in-the-loop simulation results, a platform model is bulit as the research example, and furthermore, model test and hardware-in-the-loop simulation test are performed synchronously. By this means, feasibility of the hardware-in-the-loop simulation applied in the research on the raising and lowering procedure of the bucket foundation platform, and the pumping-out-and-pumping-in method can be realized. Precision of the controlled longitudinal motion is less than ±2 degree.The final goal of this paper is to build hardware-in-the-loop simulation test system for the raising and lowering procedures of the platform, and to do the experimentation, then carefully to study the experimentation results so that conclusions are drawn at last. To build this system, the mathematic model during raising and lowering should be established firstly, then real-time control arithmetic must be carried out during test secondly, and the other part of the system also should be studied at last. So, there are three parts in this paper, which are establishment of the mathematic model(the second chapter), design and test of the hardware-in-the-loop simulation system(the third chapter), and analysis and conclusions of the experimentation results(the fourth, fifth and sixth chapter).The first chapter: based on the development of technology of the marginal oil fields, studies on the procedure of th...