Framework de apoio à decisão para avaliação das alternativas de descomissionamento de plataformas fixas de óleo e gás offshore

Abstract

Worldwide, thousands of offshore platforms are forecast to be decommissioned in the coming years. The decommissioning process is complex, costly, involves decisionmaking with conflicting objectives and generates environmental, socioeconomic, financial, safety and technical impacts. This thesis aims to propose a decision support framework for evaluating decommissioning alternatives for fixed offshore oil and gas platforms, considering the criteria for satisfying stakeholders. Initially, a systematic literature review was conducted to identify the factors that influence the decommissioning decision and build a conceptual framework for the decommissioning process. Subsequently, a decision framework was developed and applied to an offshore fixed oil platform, using the ELECTRE III multi-criteria method. The scenarios were analyzed, with different perspectives, to evaluate the ranking of alternatives in the decommissioning of a fixed offshore platform. According to the specialists' point of view, in all scenarios the best ranked alternative was to leave in place. The other alternatives varied according to each scenario, with the second place ranging between the alternative’s partial removal (leave next to the jacket) and complete removal, the third was the partial removal (land disposition) and the last place varied between complete removal and partial removal (land disposition). The sensitivity analysis of the ranking of the alternatives with the variation of the weights, preference and indifference thresholds showed no changes in the ranking. The model applied in the ELECTRE III method had low sensitivity with changes in these parameters. The main problems found in applying decommissioning alternatives in Brazil are associated with the improvement of the legal framework and gaps found in some areas of decommissioning. The decision framework can be used by stakeholders to make decisions about decommissioning, requiring a case-by-case analysis.