ABSTRACT:

This paper illustrates the issues related to ultra-deepwater installation and maintenance of the NEMO system and the spin off associated with ultra-deep hydrocarbon exploitation. NEMO (NEutrino Mediterranean Observatory) is a frontier R&D Project managed by the Italian "Istituto Nazionale di Fisica Nucleare" (National Institute of Nuclear Physics - INFN) with the purpose of building and installing a deep-sea telescope, in the Mediterranean Sea, in 3500 m water depth, to detect high-energy astrophysical neutrinos. The proposed system consist of an apparatus of about one cubic km containing an array of about 10000 photosensors which will monitor Cerenkov light produced by high energy muons. Saipem's Group of Companies, because of their wide expertise and experience in the offshore plant design, construction, installation and maintenance, has been selected to join the Scientific Community to perform the system design accordingly with the above issues. The design of the subsea telescope structure, the definition of the relevant installation procedures and the selection of instrumentation for dynamic monitoring of the structure position and of the environmental parameters is currently in progress and presents some challenging issues to be solved. The dimensions of the whole system together with the water depth at the installation site, are the most critical aspects that heavily condition the choice of the best architecture associated with the system monitoring requirements. The challenging issues related to the selected architecture versus the installation and maintenance tasks, including ROV intervention, are discussed and the background of field proven solutions and operations coming from the Offshore Industry is evidenced. Also the spin off that can be derived from the specific solutions developed for this project are presented in view of their possible application in ultra deep water subsea field exploitation. The results coming from the design of this frontier system demonstrate the possibility of installation and maintenance of complex subsea production systems like those includes subsea active processing elements thus reducing the transportation and topside facilities.

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