Steel Steep Wave Riser as an Alternative Configuration for FPSO’s Compliant Risers

Abstract

The work was focused in the chase for alternative configurations that could resist to the high FPSO motions in the Brasil’s Pre-Salt harsh wave environment, and that could also be less compliant laterally when compared to the SLWR solution. A case study was taken where an infield 8 inch SLWR configuration has been taken for comparisons. After adjusting the SSWR (Steel Steep Wave Riser) main characteristics such as top angle, buoyant section length, buoyancy modules geometry and spacing, feasible configurations have been obtained. For a configuration to be considered as feasible, a set of verifications have been carried out including extreme events, wave fatigue, vortex induced vibration and installation. The verification was performed considering several riser top connection positions and azimuths along the FPSO riser support balcony. The interference with neighboring risers has been also taken as an important issue, but was taken solely for comparison with the SLWR configurations. The installation phase has been focused including the stages of bottom connection, normal pipe lay and the connection at the FPSO. The main problems associated to the installation phase of the steep wave configuration were identified and addressed in the discussion presented. As the SSWR configuration has a fixed point at the sea bottom, two different solutions for this connection have been studied, and the final choice is described. The main differences between SSWRs and SLWRs, and the possible advantages of the SSWR configuration are discussed and a direct comparison is presented.

A numerical study on the installation configuration design of steep wave riser (SWR) in deep water

“…4 In the application of finite element method, Pereira et al established a finite element model to obtain feasible configuration of the SWR by adjusting its top angle, length of buoyancy section and geometry of buoyancy modules, which will help the FPSO resist the 1 College of Mechanical and Transportation Engineering, China University of Petroleum -Beijing, Beijing, China high motions. 5 Qiao et al obtained a set of equations to describe the motion of the SWR. The equations are established based on the large deformation beam theory and mechanics equilibrium principle.…”