ABSTRACT:

This paper provides an overview of the fuel recovery operation from inside the sunken tanker Prestige. The ship carrying some 77,000 Tm of heavy fuel broke up and sunk in 3850 meters water depth in November 2002, some 150 miles off the north-western coast of Spain. During the sinking and for a period of several months afterward a large amount of fuel was spilt ending up mainly on the shores of Galicia. Repsol YPF, though in no way connected to the vessel or its cargo, was appointed by the Spanish government to recover the fuel remaining inside the wreck. Later Repsol YPF selected Sonsub as the main contractor. The project's scope involved designing the tools required to operate at nearly 4000 meters depth - including the modification of work-class ROVs (Remotely Operated Vehicle) for operations at this depth; sealing of all remaining leaks in the wreck; and conducting a comprehensive data acquisition and research campaign that included measuring the fuel remaining inside the wreck's tanks. The project further required development, testing and installation of a safe system to perforate the wreck's deck and control the extraction of fuel, as well as testing and implementation of a novel batch extraction method using large volume aluminium shuttles to remove all mobile fuel. Introduction of an innovative core-flow technique to extract this extremely viscous fuel (3 to 4 million centipoises) from the shuttles and discharging it into a FSO (Floating Storage and Offloading tanker) was also part of the project. Finally the project involved implementation of a bio-remediation procedure to accelerate the bioremediation of the immobile fuel. The Prestige Recovery Project has won Repsol YPF the prestigious Energy Engineering Project of the Year at the Platts Global Energy Awards for 2004

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