Natural transverse vibration characteristics of jack-up riser and its applied research

摘要

In order to resolve the resonance problem of jack-up riser with drill string, the frequency equation of natural transverse vibration with compressive axial load and the length of the riser above the seabed as independent variable was derived in this paper. Then the frequency equation was solved by the Newton method, and the accuracy of the frequency calculation method without axial load was analyzed. In addition, a resonant rotating speed table of top-drive system (TDS) was made according to the relationship between rotating speed and frequency. The results show that: the method proposed in this paper is more accurate than the Rayleigh method; equation (22) is available when the length of the riser above the seabed is shorter than 30 meters while axial weight less than 90 tons; there is a nonlinear relationship between the frequencies of the riser and the length of the riser above the seabed, and the frequencies decrease with the increasing length; under the general working conditions of jack-up, the relationship between the frequencies of the riser and axial compressive load is almost linear, and the frequencies decrease with the increasing axial compressive load; the resonant frequency range of the riser with drill string depends on the length of the riser above the seabed, and the resonant frequency range is extended by the increasing length.