Enhancing Sustainability Using Multi-Criteria Decision Making in Subsea Decommissioning

Abstract Decommissioning decision-making is an integral and complex process in various industries, such as nuclear power plants, oil and gas facilities, and industrial manufacturing plants. The planned service life of many offshore oil and gas facilities is coming to an end. Decommissioning these facilities has emerged as a crucial task due to significant and uncertain expenses, high operational risks, potential social consequences, and environmental considerations related to the marine ecosystem. This paper proposes an evolving methodology to assist a sustainably oriented decision process for decommissioning the subsea infrastructure of offshore oil and gas facilities. Decision-making plays a crucial role in the search for a balance between the concerns of stakeholders, such as oil and gas companies, government bodies, environmental protection organizations, marine and coastal environmental users, and local communities. The decision problem is often complex since, most of the time, no ideal option is available to satisfy all criteria. Decision-makers can employ advanced approaches to address this problem, such as the multi-criterion decision analysis presented in this work. This methodology improves the decision-making process by ranking the various options for decommissioning subsea oil and gas assets. The model considers six criteria: Safety, Environment, Waste Management, Technical, Social, and Economic. Multiple decommissioning alternatives are compared, where groups of structures with similar technical and environmental characteristics are identified and analyzed together. The paper summarizes the application of this methodology in decommissioning different fields off the Brazilian coast, demonstrating excellent performance in helping the decision-making process. The methodology proposed addresses the growing concern about properly disposing of the decommissioned materials in an environmentally responsible manner with guidance from life-cycle assessment methods. Furthermore, attention is given to sustainability-related concerns regarding emissions generated during decommissioning operations. A set of tools was developed to help the stakeholders to have a better understanding of the results. The methodology contributes to reducing the subjectivity of the decision by assisting a project that is still conceptual to make decisions based on solid foundations raised through various databases and specialist knowledge.