Application of Mode Superposition Method in the Recoil Response of Deepwater Drilling Risers after Emergency Disconnection

This paper has considered the heave motion of floating drilling platform, seawater damping and the viscous resistance of drilling fluid discharge, established an infinite degree of freedom mechanical model and control equation of recoil response, and model reliability has been verified. On this basis, the influence of wave period, wave height, initial phase angle of emergency disconnection and tension coefficient on the characteristics of recoil response are discussed. The research results show that the actual displacement of the drilling riser recoil response can be divided into two parts: rigid displacement caused by the heave motion of the floating drilling platform and elastic deformation caused by the initial strain energy. The tension coefficient and riser wall thickness mainly affect the elastic deformation, while the wave period, wave height and initial phase angle mainly affect the rigid displacement. When the wave height increases, the collision risk between LMRP and BOP increases. The initial phase angle should be selected according to the riser recoil period and wave period comprehensively. This study is of guiding significance for the safety control of emergency disconnection of deepwater drilling riser.