Self Standing Hybrid Riser System in Waves and Current

Nowadays, the hybrid riser system concept is considered an alternative system in ultra-deep water up to 3000 meters for offshore petroleum production. Compared with other systems, the Self Standing Hybrid Riser (SSHR) proves to be a good alternative. The system is composed by three main components: a vertical riser connected to the seabed, a subsurface buoy close to the sea surface, and a flexible riser connecting the buoy to a floating production facility. Despite desirable performance of the overall concept, many problems still remain in the design of this type of riser system dealing with oil and gas production or exporting petroleum production. In the present study, dynamic behavior of a vertical riser with a subsurface buoy near the sea surface is described. Hydrodynamic loads due to currents and waves in the direction of the loads and in the transverse direction due to vortex shedding are considered. Critical points are addressed throughout time domain calculations in terms of riser vortex induced vibration (VIV) and in-line motions due to current and waves. The influence of buoy oscillations on the riser behavior is observed. For a first attempt of a developed model, comparisons have been carried out with experimental results.