Self Standing Hybrid Riser (SSHR) system is an attractive option for deepwater application. The system is composed by a vertical riser pipe coming from the sea bottom to a subsurface buoy which is placed in around one hundred meter water depth from the sea surface. It is connected to a floating production facility at the sea surface by a flexible jumper. It almost eliminates all the undesired dynamic effects from ocean waves, in addition to relief the total riser system weight from the floating platform. Recent discoveries of petroleum in ultra-deep water Pre-salt Offshore Brazil stimulated development of innovative and nontraditional riser system configurations.
The present work deals with the dynamic behavior of a SSHR system excited by sea current, waves and displacements induced by sea surface platform motions. In plane and out of plane displacements for the SSHR system is analyzed and subsurface buoy maximum motions amplitude have been observed. Effects from current drag and vortex induced forces are investigated by numerical simulations of the dynamic behavior of the SSHR system.
Analysis procedure is presented with details, and fundamentals of the semi-empirical approach for hydrodynamic drag and vortex induced forces in the riser length and subsurface buoy are described. Numerical simulation results are presented, and evaluations are conducted for deepwater condition. Maximum amplitude of vibration is observed near from to lock-in conditions, and effects of the subsurface buoy vortex induced motion (VIM) are discussed. Hydrodynamic forces previously obtained from reduced model tests are used for the numerical approach.