Research On Towing Motion Characteristics Of Integrated Composite Bucket Wellhead Platform

In view of the difficulties in the development of marginal offshore oil fields in China,this paper proposes a new offshore oil field development facility,composite bucket foundation wellhead platform combined with the design concept of bucket foundation structure.In order to verify the air-floating towing safety of the integrated composite bucket foundation wellhead platform and obtain the towing motion characteristics of the structure,this paper takes the composite bucket foundation wellhead platform with a diameter of 40 m as the research object and studies the towing motion characteristics of the structure through model test and MOSES numerical simulation,which has important guiding significance for the field construction.The main research contents are as follows:The static stability,natural period and hydrodynamic characteristics of integrated composite bucket wellhead platform are studied.The static stability curves of structures under different drafts are obtained.The proper period values of heave and swing are obtained.RAO,the amplitude-frequency response operator of structures with different drafts and waves downward,was obtained,and the mass coefficient and radiation damping coefficient were added to establish the hydrodynamic database of integrated composite bucket wellhead platform.The towing motion characteristics of structure are studied by model test and numerical simulation.The effects of wave height,wave period,structural draft,towing speed,wave direction and wind speed on foundation motion characteristics,towing cable force and air pressure are analyzed.The accuracy of numerical simulation is verified.The results show that the wave height has a significant effect on the structure towing motion.When the wave period is 10 s,it is close to the natural period of the structure,and the structure motion response reaches the maximum.The structure draft and the height of towing cable point have the main influence on the forward state of the structure during towing.Increasing speed within a certain range can improve towing stability.In actual towing,low-speed towing and running with the sea should be avoided when the wave height is higher.The towing motion response of structural cabin after failure is studied by numerical simulation.The results show that cabin connected has little influence on towing stability.The stability of the structure decreases after the leveling of damaged cabin,but it can still be towed normally under favorable environmental conditions.The towing response of structures under different irregular waves with recurrence periods of 1 year,5 years and 10 years is calculated by using numerical simulation method combined with measured sea state data in Bohai Sea,which can provide reference for actual construction.