ENGINEERING DESIGN OF DEEPWATER FREE STANDING HYBRID RISER

The free standing hybrid riser (FSHR) offers advantages over other field proven deepwater riser concepts for particular applications and has been used mostly off West of Africa. This concept has evolved in the last few years and now is drawing more attention in other deepwater provinces worldwide, such as the Campos Basin in Brazil and the Gulf of Mexico (GoM). It is basically a combination of steel and flexible risers with utilization of their advantages and hence offers unique features. This paper presents the engineering design and analysis aspects of deepwater FSHRs including key technologies and techniques. First of all, a general description and comparison of the FSHR system is presented. Secondly, the logical procedure for design and analysis of deepwater FSHRs is discussed and presented in more detail. Due to the complexity of FSHRs, different applicable design codes have been presented and discussed. Global configuration design with consideration of riser performance and its effect on component design is presented followed by major design considerations for individual components of the system. Thirdly, the analysis requirement and methodology is discussed in detail with focus on global response analysis, vortex induced vibration (VIV) analysis, buoyancy can (BC) VIM fatigue analysis, interface loads, and component analysis such as buoyancy can, tether chain system, top riser assembly, flexible jumper configuration, and riser base pile. The relationship between engineering design, fabrication and installation, which is of particular interests to this type of riser, is briefly discussed.