Advances in Deepwater Steel Catenary Riser Technology State-of-the-Art: Part II—Analysis

Abstract

The Steel Catenary Riser (SCR) concept offers advantages over other riser concepts 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 (Spars, TLPs, SEMIs, and FPSOs) in the deepwater fields of West of Africa, the Gulf of Mexico (GoM), and Offshore Brazil. As the second of two companion papers, this paper presents the state-of-the-art of key analysis techniques of deepwater SCRs while the first paper addresses the design methodology [R. Song, P. Stanton, Ref. 4]. First of all, the procedure for analysis of deepwater SCRs is discussed and presented in more detail than given in the first paper and is also illustrated in an analysis flowchart. Wave theory applicable to deepwater SCR analysis and time domain vs. frequency domain analysis approaches are described and discussed. More focus is given to the strength analysis including discussion and comparison of regular wave and random wave approaches. Attention is paid to the vortex induced vibration (VIV) analysis including discussion of modal response analysis and VIV parameter selections. For SCRs on semisubmersibles and FPSOs, vessel heave-induced VIV needs to be taken into account, and a corresponding time-domain approach is presented. Similarly, for Spars and deep draft semisubmersibles, vortex-induced motion (VIM) fatigue damage of SCRs is discussed in more detail. Particular attention is also given to the analysis of SCR compression in the touch-down zone (TDZ) and corresponding acceptance criteria are presented. The application of fracture mechanics to engineering criticality assessment (ECA) is explored. Two examples of deepwater SCRs corresponding to a semi and a Spar are given to illustrate the presented methodology.

Modeling the Effects of Steel Catenary Riser (SCR) Wall Thickness on Its Structural and Fatigue Performances for Wave-Induced Load

“…Contemporary SCR designs put into consideration some critical parameters while also allowing for the unexplained variances that could exist within these parameters (Song, R. S., 2009). Typically, the design considerations are encapsulated in the following: a) Load conditions: All of these are captured in Table 1.…”

Vessel relocation strategy for multiple steel catenary riser fatigue damage mitigation

“…Steel catenary riser (SCR) systems are used to transport hydrocarbon production-related materials between the seabed and the host floating platform. SCRs are the most attractive riser solution likely because of their simplicity, robustness, and lower procurement costs [1][2][3][4][5][6]. A significant challenge with SCR application is the high stress and fatigue damage incurred around its critical sections: the hang off (HO) and the TDZ [5,[7][8][9], which are depicted in Figure 1.…”

On the Fatigue of Steel Catenary Risers

“…There is, therefore, a need to ensure that the integrity of riser systems is not compromised; that is, ensuring high fatigue life in performance. In West African deepwater, for example, steel catenary risers (SCR) are commonly used because of the prevalent conditions, though fatigue remains a challenge [3]. SCR is a costeffective alternative for oil and gas export and for water injection lines on deepwater fields, where large-diameter flexible risers present technical and economic limitations [4].…”

“…This is due to their relatively low cost, conceptual simplicity, significant structural capacity, and ease of fabrication and installation. However, their fatigue response has been a concern to the industry, especially in West Africa [3]. SCR fatigue damage can be caused by vortex-induced vibration (VIV) and vortex-induced motion (VIM) at the touch-down-point (TDP) [3].…”

“…However, their fatigue response has been a concern to the industry, especially in West Africa [3]. SCR fatigue damage can be caused by vortex-induced vibration (VIV) and vortex-induced motion (VIM) at the touch-down-point (TDP) [3]. Fatigue of SCR at TDP has been one of the most challenging problems in deep water due to interactions with the seabed [5].…”