MARIN and Oceânica work in tandem on project
MARIN and Oceânica
recently joined forces to study the tandem offload- ing operation of the first
FPSO in the Gulf of Mexico for the Petrobras Cascade/ Chinook development. MARIN performed the
model tests in its deep- water Offshore Basin and Oceânica, the numerical analysis in Brazil. Report outlines this unique and successful partnership.
Daniel Cueva (Oceânica) & Jaap de Wilde
j.dewilde@
marin.nl
Cascade and Chinook are located in the Walker Ridge block, around 300 km (180 miles), south off the Louisiana coast. The FPSO will have a 80,000bpd processing capacity and a 16 MMcfpd natural gas export capacity. Featuring a disconnectable turret buoy, the FPSO can move offsite during severe weather events, such as hur- ricanes. It is moored by a polyester mooring system, linked to torpedo piles and vertical loaded anchors. Crude oil will be offloaded via a shuttle tanker in tandem arrangement and a tugboat will be available at the
stern of the shuttle tanker during the offloads. Tandem offloading requires a thorough understanding of the relative motions of the shuttle tanker behind the FPSO in all weather conditions. Obviously, loads in the hawser should remain within safe limits and the shuttle tanker should remain at a safe distance from the FPSO. The combination of model tests and numerical simulations, as well as the cooperation between the two organisations proved very successful in this project.
The figure shows a bird’s eye view of the relative motions of the shuttle tanker behind the FPSO, as measured in the Offshore Basin. The green, yellow and red sectors indicate the levels of proximity, with the following actions from the captain: Green: The shuttle tanker is allowed to swing freely within the green sector. The limits for normal offloading operations are 45 degrees of relative heading from the FPSO centre line. Yellow: The shuttle tanker is allowed to remain in the yellow sector for enough time to allow the captain to attempt to bring the vessel back to the green sector. Red: When the vessel reaches the red sector, the captain should immediately execute the emergency disconnection. Under no circumstances should the shuttle tanker remain in this sector.
report 29
83907
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