A multi-attribute decision analysis for decommissioning offshore oil and gas platforms

Abstract

Abstract The 27 oil and gas platforms off the coast of southern California are reaching the end of their economic lives. Because their decommissioning involves large costs and potential environmental impacts, this became an issue of public controversy. As part of a larger policy analysis conducted for the State of California, we implemented a decision analysis as a software tool (PLATFORM) to clarify and evaluate decision strategies against a comprehensive set of objectives. Key options selected for in-depth analysis are complete platform removal and partial removal to 85 feet below the water line, with the remaining structure converted in place to an artificial reef to preserve the rich ecosystems supported by the platform's support structure. PLATFORM was instrumental in structuring and performing key analyses of the impacts of each option (e.g., on costs, fishery production, air emissions) and dramatically improved the team's productivity. Sensitivity analysis found that disagreement about preferences, especially about the relative importance of strict compliance with lease agreements, has much greater effects on the preferred option than does uncertainty about specific outcomes, such as decommissioning costs. It found a near-consensus of stakeholders in support of partial removal and “rigs-to-reefs” program. The project's results played a role in the decision to pass legislation enabling an expanded California “rigs-to-reefs” program that includes a mechanism for sharing cost savings between operators and the state. Integr Environ Assess Manag 2015;X:000–000. © 2015 SETAC Key Points Economic and environmental impacts associated with alternative decommissioning options can best be investigated with a decision model. The decision model created for this project, PLATFORM, was used to derive the first quantitative estimates of cost savings from an artificial reefing option, fish production association with the platform habitat, and worst-case air emissions from the complete removal option. A multi-attribute analysis showed that stakeholder preferences for strict compliance (complete platform removal) must be at an extreme level for any combination of preferences to result in a choice for complete removal, whereas all other preference values resulted in a choice for partial removal and artificial reefing.