Research On Motion Response Of Cylinder Offshore Oil Platform And Mooring Line Force In The Process Of Floating Shipbuilding

With the rapid development of global economy, human's demand for the fossil energy is still high. However, with the exhaustion of oil and gas resources on the land and near the offshore, exploiting the deep sea is becoming an inevitable trend, because it contains rich oil and gas resources. China has a vast sea area, and huge marine oil and gas resources. But the development technical level of the resources is not high, and there is a big gap in the advanced level compared with other countries. The development and manufacture of drilling platform exploiting the deep sea resources is of great significance to national energy security.A new manufacturing method of floating shipbuilding is applied in the development of the first cylindrical offshore platform SEVAN 650 all the world, duo to the special manufacturing condition and the difficulty of launching. The method takes the buoyancy of water as the support, and takes platform which has been built as a manufacturing base, then the whole drilling platform is completed with the form of "layered manufacturing and layer-by-layer accumulation".In the process of floating shipbuilding, the cylindrical platform is bounded by the dock mooring system and its motion is complicated. The mooring system has a significant effect on manufacturing precision in the conventional situation and the mooring safety in the harsh environment. So it is very important to study the movement response of platform and the force of dock mooring system in the process.This paper takes the cylindrical offshore platform as the research object, and studies the movement response of platform, as well as the mechanical performance of different forms of mooring system to propose the improvement program. The main work of this paper is as follows:(1) Use AQWA to build the finite element model with the 20m depth of water to study the hydrodynamic performance of the platform in the frequency domain. According to the result, summarize the movement regularity of the platform in waves, and provide a basis for the research on platform and mooring lines in time domain.(2) In time domain, simulate the platform's movement response and the mooring lines' force in the different time periods of conventional situation, and analyze if the result meet the precision.(3) Based on the simulation of dock mooring system in the extreme environment, obtain the maximum of wind speed which the mooring system can resist. Then considering the mooring lines'force, optimize the original mooring system and propose a new system, which can make the platform safe under the severe condition to avoid the accident and economic losses due to the mooring lines'rupture.This paper has researched and analyzed the dock mooring systems of floating shipbuilding. The achievements can enrich the theory of floating shipbuilding, provide the theoretical basis for the design of mooring system, and improve the manufacturing technology of giant offshore platform to some extent.