Feasible SCR Configuration from FPSO with Large Motions, by Applying Residual Curvature Methods

Abstract

This paper describes an alternative and innovative solution to Steel Lazy Wave Risers (SLWR) in order to allow the rigid riser be designed in a free hanging configuration from a floater with large hang off vertical motions. This work demonstrates that the residual curvature method can reduce the stress at the touchdown zone (TDZ) within acceptable limits and improves fatigue life when compared to a Steel Catenary Rigid (SCR). The state-of-art concept eliminates the necessity of buoys in a SLWR concept. Further, there will be saving in installation time, this combined reduces the CAPEX to develop new projects, making it a very attractive solution in recent market scenario. The results for Brazil offshore scenario at Santos Basin and in Gulf of Mexico, in a water depth of 2100m indicate a considerable reduction on the stress at the TDZ within acceptable limits. Fatigue results indicate a slight improvement when compared to a SCR in a free hanging configuration. The fatigue performance for the Gulf of Mexico condition has sufficient fatigue life. However, it has potential margin to be developed in the future and achieve better results. The new concept was evaluated numerically through a comprehensive load case matrix contemplating extreme and fatigue analysis. Results indicated the feasibility of the solution, making it a considerable alternative to replace SLWR in harsh environments.