Abstract

The wreck of the 'Prestige' oil tanker resulted in one of the worst natural disasters occurring in Spain's recent history. The oil tanker, carrying 77,000 Tm of fuel oil, was affected by a storm near the north-western coast of Spain; after some days of uncontrolled sailing, the ship broke in two and sank, in some 4,000 m. of water, with an unknown quantity of the cargo still remaining in its tanks.

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. Subsequently, Repsol YPF selected Sonsub Limited to be the main contractor. Due to the urgent need to extract the remaining fuel, and avoid further environmental damage, Repsol YPF and Sonsub were obliged to design and develop a group of innovative tools, which allowed the operation at such depths, within a very short time frame.

This paper describes the upgrading, testing and approval of Sonsub's 150 HP work class Innovator ROVs to permit operations to be performed in water depths up to 4,000 meters, with particular focus on the offshore tasks that were to be carried out to recover the fuel oil in the wreck of the 'Prestige'.

These operations required the use of innovative deepwater equipment and procedures, both due to the water depth and the atypical activities that needed to be performed, including the involvement of numerous vessels on the surface, simultaneous ROV operations in nearly 4,000 meters, the tapping onto the wreck's tanks, the transfer of extremely viscous fuel into specially designed shuttles and their final recovery and offloading into a dynamically positioned FSO.

The Prestige Recovery Project has won Repsol YPF the prestigious Energy Engineering Project of the Year at the Platts Global Energy Awards for 2004.

Introduction

The single hull tanker 'Prestige', at the time in the hands of the Greek ship-owner 'Mare Shipping Inc.', reported difficulties on November the 13th, 2002, while in a storm 21 miles off the Spanish North coast. Soon after, the tanker began to spill its cargo of some 77,000 Tm of heavy oil fuel. Nearly a week later, on November 19th, 2002, the ship broke in two and sank, some 240 km from the North West coast of Spain. Two shipwrecks were left: the bow section sank to 3,830 meters while the stern section came to rest in 3,565 meters of water.

Among others, the main challenge of the project was associated with the heavy-duty works to be carried out in 4,000 meters of water particularly the risk management associated with a complex operation involving new technology and the strict need to protect the environment. Work-class remote operated vehicles (ROVs) rated for operations in 4000 m did not at that time exist, so two models were selected for the upgrading, Sonsub's Innovator and Thales´ G3 series.

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