Steel Catenary Riser with Residual Curvature in Deepwater and Harsh Environment
Master thesis
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https://hdl.handle.net/11250/3018547Utgivelsesdato
2022Metadata
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Sammendrag
The exploration and production of oil and gas are still high in demand. With theadvancement of subsea technology, it is possible to move into deeper waters andharsher environments. It highlights the importance of finding riser configurationsthat is suitable but also cost-effective. This thesis aims to find a riser configurationthat can handle the large vessel motions of the Floating Production, Storage andOffloading (FPSO) in a remote, deepwater and harsh environment.
The conventional Steel Catenary Riser (SCR) has been a favored concept for deepand ultradeep water developments. However, the SCR is very sensitive to large vesselmotions, impacting the downward velocity at the hang-off point. This translates toa higher velocity in the Touch Down Zone (TDZ) that can induce excessive levels ofstress and fatigue.
An alternative that has been considered is the implementation of residual curvaturesections in the riser using the Residual Curvature Method (RCM). These sectionscreate a small deformation in the pipe that works as triggers for lateral bucklingand aids in absorbing compressive forces generated. A comparison between theconventional SCR and the Residual Curvature Steel Catenary Riser (RCSCR) isperformed to evaluate how the residual curvature affects the response in the TDZ.
According to previous works, the conventional SCR with a coating is not able tocope with a downward velocity above 2.33 m/s. The implementation of ResidualCurvature (RC) to the riser showed that it could cope with downward velocities upto 3.35 m/s at the hang-off point. Moreover, the fatigue performance was analyzedfor wave-induced fatigue. Neither the SCR nor the RCSCR had an expected fatiguelife above the acceptance criteria of 250 years.
Overall, this thesis has shown that the RCSCR improved the strength performancein the TDZ and improved the riser’s ability to cope with large vessel motions. Forfatigue performance, the RCSCR did not meet the design requirements and stillrequires more study.
Keywords: Residual Curvature Method, RCM, Steel Catenary Riser, SCR, Extreme Response Analysis