Advances in Deepwater Steel Catenary Riser Technology State-of-the-Art: Part I — Design

Abstract

Steel Catenary Riser (SCR) concept offers great advantages over others and has been widely deployed worldwide. The first deepwater SCR was installed in the Gulf of Mexico in 1994. Since then, more than 100 SCRs have been installed for many types of deepwater floaters (SPAR, TLP, SEMI, and FPSO) in the deepwater fields of West of Africa, Gulf of Mexico, and Offshore Brazil. This paper presents the state-of-the-art of the design methodology of deepwater SCRs. First of all, the design procedure is discussed and is also illustrated in a flowchart. Material selection is discussed in terms of weldability, corrosion resistance, and effect on riser performance. Different wall thickness sizing criteria and design codes are compared. The three most commonly used types of SCR hang off system (flex joint, stress joint, and pull tube) are presented and their application limitations are discussed. Strakes and fairings are discussed and compared as the vortex induced vibration (VIV) suppression devices. Focus is given to the design of SCR global configuration and riser routing. Effect of different floaters on the global configuration design is discussed and illustrated through examples. Thermal performance requirements versus riser global response are traded off. Corrosion, thermal insulation, and anti-abrasion coating materials available for deepwater SCRs are summarized. SCR cathodic protection design methodology is summarized and a design guideline is given. The number one challenge of deepwater SCR design is fatigue. Selection of SN curve, effect of sweet and sour service on fatigue performance, stress concentration factor (SCF) calculation, full scale fatigue testing requirements, application of fracture mechanics to engineering criticality assessment (ECA) is discussed. Fatigue mitigation design is also explored supported by examples. Design of the SCR subsea interface to flowline and pipeline is presented.