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

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.

Considerations in evaluating potential socioeconomic impacts of offshore platform decommissioning in California

“…Second, stakeholders' and user groups' preferences have been described (e.g., Rothbach ) but not evaluated systematically. However, the PLATFORM model's multi‐attribute analysis features allows for an examination of the implications for decision making of differences in stakeholder perceptions and values (Henrion et al this issue).…”

“…Despite those constraints, one may consider the likely direction of each decommissioning option's impacts on marine resources. For example, Henrion et al (this issue) include the predicted qualitative type, direction, and relative magnitude of impacts on marine birds, marine mammals, and benthic communities, whereas Pondella et al (this issue) present the results of quantitative modeling of how the biological production associated with platforms would be affected by each option. In terms of how decommissioning's effects on marine resources would affect user groups, complete removal may allow access to small areas of the ocean, but the impacts on certain valuable species may outweigh this potential gain in area if increased fishing pressure reduces population size.…”

“…These options included 2 use options (complete removal and partial removal as part of conversion to an artificial reef) and 1 disposal option (onshore dismantling). For additional details, see Henrion et al (this issue).…”

“…Despite this, the quantitative data we were able to identify, combined with the qualitative identification of the direction of user preferences among decommissioning options and the relative magnitude of options' impacts, provided valuable input to the mathematical decision model (PLATFORM) and the multi‐attribute analysis it enabled (Henrion et al this issue). PLATFORM's multi‐attribute analysis module enables the integration of both quantitative and qualitative attributes and provides users the ability to investigate how different valuations of a range of costs and benefits (e.g., fish production, marine mammal impacts, air emissions, socioeconomic impacts) would affect the choice among options.…”

A semi-automated approach to generate 4D/5D BIM models for evaluating different offshore oil and gas platform decommissioning options

“…Over the next 30 years, almost all the 470 offshore installations in the North Sea's UK Continental Shelf, will need to be decommissioned, according to the UK Oil & Gas Economic Report (2013). Twenty-seven offshore oil and gas platforms in southern California will be decommissioned by 2030 as the platforms will reach the end of their useful production lifetimes (Henrion et al 2015). In Malaysia, the decommissioning activities for fixed offshore platforms are expected to rise significantly.…”