Subsea Production Risers
This chapter compares four types of production risers: steel catenary risers (SCRs), top tensioned risers (TTRs), flexible risers, and hybrid risers. The SCR is a cost-effective alternative for oil and gas export and for water injection lines on deepwater fields, where the large-diameter flexible risers present technical and economic limitations. An SCR is a free-hanging riser with no intermediate buoys or floating devices. TTRs are used as conduits between dynamic floating production units and subsea systems on the seafloor, for dry tree production facilities such as spars and TLPs. TTRs are individual risers that rely on a top tension in excess of their apparent weight for stability. TTRs are commonly used on TLPs and spar dry tree production platforms. Flexible risers are one of the common types of production risers. Theymay be deployed in a variety of configurations, depending on the water depth and environment. Flexible pipes have traditionally been limited by diameter and water depth. Hybrid risers (HRs) consist of a vertical bundle of steel pipes supported by external buoyancy. Flexible jumpers connecting the top of the riser and the vessel are used to accommodate relative motion between the vessel and riser bundle.