Research On The Mechanics Problem Of Marine Drilling Riser

Being one of the key equipment in marine drilling,the drilling marine riser is also the vulnerable components.The deeper analysis on its natural frequency and dynamic response has great significance to the study of its strength,stiffness and stability.At present,the researches on the natural frequency and dynamic response of the riser are mainly concentrated on its size and the top tension.Because the way of its movement in the sea belongs to a large displacement and small deformation in the sea and the drilling moves company with the riser.Therefore,the influences of drill string quality on the natural frequency and dynamic response of the marine riser is analyzed necessarily.The natural frequency calculation formula is derived,through establishing the mechanical model of the riser.The influence of drill string quality and the top tension on the natural frequency of the riser is calculated and analyzed.The results show that the ignorance of the drill string quality on the natural frequency of the drilling marine riser can result in a greater error,the maximum relative error is about 6.2%.After the dynamic response equation of the marine riser is derived,the influences of wave period and wave height on the dynamic response are also calculated and discussed.The research shows that the dynamic response of the drilling marine riser can be caused by a large error,with the maximum relative error being about 1.96%,when the quality of the drilling marine riser is neglected.The natural frequency of the drilling marine riser is analyzed by the finite element method,and the case of the riser is in safe working condition.The error of the dynamic response of the riser is 7.05%.The stress of the marine riser in x,y,z axis is concentrated on different places and the maximum stress is 347 MPa,when the bottom tension is considered.The stress concentration is also changes,when the angle of the bottom hinge is changed.