SCR Fatigue Feasibility Prediction for Deepwater FPSO Applications

Abstract

Many of the recent offshore oil and gas discoveries in the world have occurred in deep waters, at locations far away from the existing subsea infrastructure. Floating Production Storage and Offloading systems (FPSOs) are the preferred field development solutions for those locations with mild and moderate environments. The simplest fluid transfer system between the seabed and the FPSO is a simple catenary configuration, with Steel Catenary Risers (SCRs) as the preferred solution for deep water, high pressure and high temperature applications. This paper introduces an effective engineering SCR fatigue screening methodology for FPSO applications. The focus of this study is to better understand SCR fatigue performance at Touch Down Point (TDP) and develop a simple but reasonable correlation between FPSO porch motion and the riser dynamic stress response at TDP. This methodology enables one to perform the porch motion statistics analysis and the riser dynamic response analysis independently. By using the wave screening approach, SCR fatigue feasible map can be effectively developed. The paper presents an example performing the fatigue screening evaluation. SCR feasibility design flow chart for FPSO application is also addressed. Particular for FPSO application in a new development, the fatigue feasibility prediction approach along with the strength feasibility check can help the project make the informative decision on the overall FPSO and riser system selection at the early stage of the development.