Double Catenary Offloading Lines for Deepwater Fields

Abstract

The use of non-weathervaning floating production units is found feasible for fields in the deep waters of West Africa. The lack of pipeline infrastructure in these remote areas requires export of produced fluid from an offloading system. The transfer of product from the production vessel to offloading buoy is carried out by large diameter suspended flexible flow-lines. The flow-lines are configured in a double wave shape, "W" concept, by introducing distributed buoyancy along the middle section of the lines.The paper presents an alternative concept, a naturally suspended double catenary ("U" configuration) rigid steel flow line. A preliminary, but comprehensive, study was conducted, which considered strength and fatigue performance, technical merits and demerits, economic gains and losses, and safety and reliability concerns between the two concepts. The results of the study confirmed the feasibility and potential savings of the proposed "U" concept.

Fatigue Analysis of the Oil Offloading Lines in FPSO System under Wave and Current Loads

“…However, for practical OOL structures in FPSO offloading systems, related fatigue analysis and design optimization research are insufficient. Chaudhury [8] proposed a "U"-type oil pipeline and made a comparative analysis of the "U"-type oil pipeline and the "W"-type oil pipeline, including strength characteristics, fatigue characteristics, economic advantages, etc. Through this research, it was found that the "U"-type oil pipeline is superior to the "W"-type oil pipeline in fatigue behavior.…”