Design And Research Of Mooring System For Oil And Gas Resource Development Support Platform

In "Made in China 2025",it is clearly pointed out that in the field of marine engineering equipment and high-tech ships,it is necessary to vigorously develop offshore operational support equipment and its key systems and special equipment.At the same time,with the development and construction of deep-sea oil and gas drilling and production equipment,oil and gas drilling in the South China Sea requires a large supply of materials,and it is difficult to meet economic and efficiency requirements by relying on distant land recharge.Therefore,while vigorously developing oil and gas drilling and production equipment,it is urgent to develop a large-scale logistics supply and support platform for oil and gas resources development to meet the living,medical insurance,material transfer,and storage supply necessary for the development of ultra-long-range marine oil and gas resources.Such comprehensive functions have obtained favorable guarantees for the development of offshore marine resources.A new type of offshore engineering equipment such as the “Oil and Gas Resource Development Support Platform” came into being.Due to the working nature of this new type of offshore equipment,it will be moored in harsh sea conditions for a long time,subject to the complex and variable wave load.In this extreme sea condition,the mooring positioning capability of the platform is particularly important.It is necessary to analyze the motion response of the platform and the fatigue performance of the mooring line.This paper mainly studies the following aspects:1? The hydrodynamic model is established according to the profile and quality information of the platform;the frequency domain analysis is carried out on the platform in the unit regular wave,and the hydrodynamics parameter such as additional mass,radiation damping,first-order wave force transfer function and motion response amplitude operator are obtained;The mooring system of the platform was preliminarily designed.Based on the frequency domain analysis,the time domain nonlinear coupling analysis of the platform mooring system was carried out.The time history curve of the motion response of the mooring system and the tension response of the mooring line is calculated in a sea state with a typhoon once in a hundred years.Analyze the influence of different angles of wind,waves and flow on the motion response of the platform mooring system and the tension response of the mooring line;The mooring performance of the initial mooring scheme under three given conditions was calculated.2? Based on the initial mooring scheme of the platform,the mooring scheme is optimized by calculating and analyzing the influence of different mooring parameters such as hydrodynamic coefficient of mooring line section,material distribution of mooring line,length of mooring line,arrangement angle of mooring line,number of mooring lines,asymmetric distribution of mooring lines on the mooring performance of the platform.For the optimized platform mooring scheme,the platform motion offset and the tension safety factor of the mooring line are calculated.The results show that the mooring performance of the optimized platform mooring system has been significantly improved,which can meet the actual engineering requirements.3? The fatigue performance of the platform mooring system was analyzed.The mooring line with the largest tension response was selected for fatigue calculation.Based on the principle of rain flow counting method,the tension time history curve is statistically processed by Matlab programming to obtain the fatigue load spectrum under each short-term sea condition.Based on the T-N curve and the Miner linear cumulative damage theory,the total fatigue damage and fatigue life of the mooring line are calculated.The calculation results show that the fatigue performance of the designed platform mooring system meets the requirements of the specification,and the fatigue performance of the steel cable is obviously better than the fatigue performance of the steel chain,and the fatigue damage of the mooring line mainly occurs in the steel chain part.