Characteristic analysis on transverse coupling vibration of offshore drilling riser-drilling fluid

Based on the vibration of drilling riser and drilling fluid in the upward return flow state, the differential equation of transverse coupling vibration has been deduced. Via the equation solving, the dynamic response expression of coupling vibration and the maximum vibration displacement of riser in the coupling vibration have been figured out. Besides, the effects of top tension, riser wall thickness, upward return flow rate of drilling fluid, water depth, wave height and wave period on the transverse vibration displacement of riser have been discussed. According to the results, the maximum transverse vibration displacement of riser, which was calculated with consideration of the drilling fluid flow, is greater than the calculation result when the flow of drilling fluid is not considered; the maximum transverse vibration displacement decreases as the top tension and water depth increase, and increases as the return speed of annular drilling fluid and wave height increase; when the changes of riser wall thickness and wave period cause the transverse vibration inherent frequency of riser to be close to the transverse vibration frequency of wave, the transverse vibration displacement of riser will sharply increase. That has certain reference value to the safety design and assessment of riser.