Steel catenary risers (SCRs) are one of the most popular and cost effective types of risers for deep water field developments. There are different complex issues for engineering of riser systems, with fatigue design, particularly in the touch down area, one of the most challenging for SCRs. Traditional fatigue designs, which are mainly based on the static response of risers lying on linear seabed springs, usually lead to overly conservative results. In general, SCRs are known as dynamic and fatigue sensitive structures. In this paper, dynamic and static responses of a particular SCR system are investigated. The main aim of this pilot study is to explore the usefulness of the DAF (dynamic amplification factor) approach for dynamic response of SCR systems, which are basically nonlinear structural systems. The sensitivity of the DAFs to some of the key input parameters is investigated with the main parameters considered being: amplitude of the vessel motions, period of the vessel motions and soil stiffness. It is shown that vessel motions (amplitudes and periods) can significantly influence the DAF, while the soil stiffness has no major effect on it.
In the last two decades, oil and gas exploration and production in deepwater offshore fields have increased and have moved into deeper waters (more than 2000 m in the Gulf of Mexico). The deepwater developments are pushing riser technology to the limit and steel pipes, rather than flexible pipes, are now the most common approach. Steel catenary risers (SCRs) are regarded as one of the most cost effective types of risers among the different riser concepts, allowing large diameter or production from remote wells. Different engineering issues exist for SCRs when used in deepwater and fatigue design is the most complicated challenges (Campbell, 1999; Aggarwal et al., 2007).
