Research On Hydrodynamics Of Blister Of Column And Mooring And Riser System Of Seme-submersibles

The rapid development of social economy has brought about increasing demand for petroleum resources,while the amount of land-based oil resources has been shrinking,the exploit of petroleum resources is gradually shifting from offshore to deep sea.So semi-submersible platform is becoming one of the most important equipments for the exploit of offshore oil and gas fields,for the advantage of excellent hydrodynamic performance,small motion response,strong anti-wind and wave capacity,large deck area and loading capacity and it requires less initial investment.Therefore,the study of semi-submersible production platform and its mooring and riser system is of great significance to the exploit of deep-sea oil and gas resources.Combining with the project from the Ministry of Industry and Information Technology,the hydrodynamic performance and mooring system of 2300 m Location in South China Sea of a four-pontoon semisubmersible production platform is researched,through model test and potential theory.Furthermore,blisters of the column are added along the longitudinal direction of a platform to study the influence of blisters on the hydrodynamics of semi-submersible through model tests and numerical simulation.The hydrodynamic performances of the semi-submersible production platform and its mooring and riser systems have met the requirements.Under operational sea conditions,the maximum heave motion response is 2.08 m and the maximum horizontal drift distance is 25.37 m,only 1.10% of the water depth,the maximum mooring cable force is 5.35 E +06 N with the safety factor of 4.09.Under survival sea conditions,the maximum heave motion response is 10.23 m and the maximum horizontal drift distance is 83.59 m,3.63% of the water depth,the maximum mooring cable force is 10.579 E +06 N with the safety factor of 2.06.Blisters are commonly attached to the columns in the longitudinal direction to improve the performance of semi-submersibles.In order to investigate the influence of the blister and its section shape on the hydrodynamic performance of a semi-submersible,numerical simulations and model tests were conducted to comparatively analyse the results of the natural periods,damping coefficients,motion RAOs,mean drift forces,and motion response in irregular waves.The results showed that,the longitudinal blisters of column can reduce the longitudinal mean drift force of the platform and the RAO in pitch direction.The motion response under extreme sea conditions is improved.The section shape of blisters has no influence on the hydrodynamic performance of the semi-submersible.