Decommissioning offshore oil and gas production systems have been progressively increasing the concern of the industry, government and interest groups through the last years. There are at least two reasons for this sudden regard. First, it is the maturing of several oil and gas fields around the world in recent years. Second, it is the growing impact of environmental concerns in international affairs. Despite several works published address to some techniques and to potential problems and risks related to decommissioning offshore oil and gas production installations, its procedures are in some extent an innovative issue, especially in the case of deep-water fields such as the Brazilian ones. Therefore, the motivation of this paper is the novelty of the subject in Brazil, since the national industry is just beginning to deal with the end-of-leasing obligations, which involve decommissioning operations, and the governmental regulatory agency is filling the current gaps in the official guidelines. The main ambition is to stimulate debate about pertinent issues. 37813793Thornton, W., The Cost Denial (1998) Oil and Gas Journal, 58 (11)Brent Spar Dossier: The Story, Photographic Record, Feature Stories, Press Releases and Technical Data, , www.shell.com/uk-en/directory/0.4010.25268.00.html, [On-line], Site: [01/2001]Meenan, P., (1998) Technical Aspects of Decommissioning Offshore Structures, Article from Decommissioning Offshore Structures, , SPRINGER-VERLAG, London, Great Britain. 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