Decommissioning of Subsea Equipment – A Technical Approach Through the Multicriteria Analysis Methodology

Abstract Decommissioning of offshore subsea systems refers to the safe disposal of oil and gas exploration and production structures and their respective subsea components after the end of the production phase of a field. In addition to different parameters, determining the most suitable decommissioning alternative for subsea structures becomes effective when indicators defining the technical aspects are considered. A multicriteria decision analysis methodology developed by a COPPE/UFRJ research group is effective in this context. Under the technical criteria, through matrices of influencing factors versus activities and risk level assignments, this paper aims to evaluate the technical feasibility of executing the activities inherent to the decommissioning alternatives based on the Operation Complexity and Technological Risk subcriteria. A case study of the decommissioning of a subsea system in Brazil was analyzed to elucidate the methodology. The decommissioning alternatives were divided into two groups – total and partial removal – and four alternatives were considered. The results show the effectiveness and robustness of the methodology by the influence of different technical parameters. In addition, this work contributes to applying the method in various scenarios and serves as a preliminary basis for decommissioning projects using multiple criteria.