Weight Optimized SCR: Enabling Technology for Turret Moored FPSO Developments

Steel catenary risers (SCRs) used in conjunction with a turret moored FPSO in deepwater environments present significant design challenges. The large vertical motions at the FPSO turret induce severe riser response. This results in difficulty meeting strength and fatigue design criteria at the Touch Down Point (TDP) and at the riser hang off location. It is typically considered challenging to achieve feasibility for a conventional SCR application on a turret moored FPSO. Previous industry work for an SCR application used with other floating hosts has demonstrated that SCR strength and fatigue response can be improved using heavy and light coatings strategically placed along the riser [1]. An optimization study is performed, based on previous industry work, which demonstrates that a weight optimized configuration can enable the application of an SCR on a turret moored FPSO. The effect of adding different coatings along the length of the SCR is discussed. The position, length, and density of the coating type are varied to determine an optimum configuration for both strength and fatigue response. This paper will also discuss observations which may help explain why weighted sections can improve SCR response at the critical area.