PROJECT BACKGROUND

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The majority of oil and gas production in European waters takes place from fixed platforms that normally comprise of a steel structure (jacket) permanently anchored (through a series of piles) to the seabed that supports an above sea level topside, composed of different modules for accommodation, power generation, pumping and initial product processing etc. (see Figure 1, North Sea Buzzard offshore platform complex and Figure 2, artists impression of the Shell Shearwater platform support jacket and topsides).

The need for this project arises from the fact that the older offshore installations were designed to earlier, since superseded, technical standards and their conditions have significantly deteriorated during service. Historically much of the inspection and non destructive testing (NDT) has been on the top-side, pressure and structural components and comparatively little sub-sea NDT and inspection has taken place on the vital support jacket structure, many of which have now exceeded their design life.

There is little if any routine NDT carried out on critical sub-sea welds in offshore support structures because current NDT equipment and techniques do not currently lend themselves to be applied sub-sea below depths of about 25 - 30metres and those cases are exceptional and rely on divers applying visual inspection and electromagnetic techniques for surface weld examination. The operating oil companies, under the encouragement of the regulatory authorities, are committed to reducing diver operations because of safety issues [recent Norwegian case awarded €3.7million compensation to 3 divers, shortage of divers and cost. Diver operations are both depth and time limited and there is now a clear case for ROV applied NDT techniques to be used in order to help prolong and extend the operational life of European oil and gas field reserves.