Effective Riser Solutions for a Deepwater FPSO

Abstract

With the recent increase of discoveries in the deepwater Gulf of Mexico (GoM) and the rapid deployment of deepwater floating production systems, the design of dynamic risers to produce and export to and from these FPS has quickly evolved in complexity and variety. As one of the attractive solutions for the development of these deepwater discoveries, the Floating Production, Storage and Offloading (FPSO) system offers a serious challenge to the riser system designer. This paper presents detailed results of a three steel risers systems design study to a turret moored FPSO system in 1,370 meters (4,500 feet) water depth in the GoM. The three riser systems considered are the Steel Lazy Wave Riser (SLWR) system, the Tension Leg Riser (TLR) system and the Single Leg Hybrid Riser (SLHR) system. The three riser concepts are shown to be feasible. The paper shows that for the diameter, number of risers and water depth considered, the SLWR is the preferred option. However, under different parameters, the TLR or SLHR may be preferred since they fully decouple the steel portion of the riser from the vessel motions via flexible jumpers. Very often, riser feasibility can only be demonstrated by doing a complete and thorough evaluation as demonstrated in the paper. The results of this paper demonstrate that steel riser options are available and present effective solutions for use on an FPSO system in the GoM.