A decision support framework for evaluation of decommissioning alternatives for fixed offshore oil and gas platforms
Decommissioning option. Fixed offshore platforms. Ranking of alternatives. Decision model. ELECTRE III
Worldwide, thousands of offshore platforms are forecast to be decommissioned in the coming years. The decommissioning process is complex, costly, involves decision-making 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 varying between the alternatives partial removal (leave at sea and take to land) and complete removal, the third was the partial removal (take to land) and the last place varied between complete removal and partial removal (take to land). 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 lack of robustness in 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. In addition, there should be more partnerships between universities and companies in the offshore industry, for the development of new research about decommissioning of offshore platforms.