Marcelo Igor Lourenço De Souza

Decommissioning poses a challenge for decision-makers. As an aspect of decommissioning that is not explicitly outlined in regulations, waste management for decommissioned materials is a special challenge. In Brazil, a large amount of the decommissioned subsea infrastructure is composed of flexible pipelines, with interlocked structures that increase the recycling challenge. This study identified two technological routes to dismantle the pipes. These routes (A and B), consisting of processes centered on the shredding and the manual dismantling of the pipes, respectively, were analyzed through a comparative Life Cycle Assessment (LCA) study. This study offers valuable insight into the waste management of decommissioned subsea infrastructure by quantifying the potential environmental impacts associated to the two main pre-processing strategies for the recycling of decommissioned flexible pipes in Brazil. Each route presented different levels of mechanization, energy consumption, productivity, labor intensity, types and levels of occupational hazards and recycling options for the resulting polymeric materials. The results from this study indicate that Route B is more aligned with the principles of a circular economy, enabling the mechanical recycling of 98% of the polymeric material and presenting substantially lower potential environmental impacts. In particular, Route B represents approximately 9.6% of the global warming impact (kg CO₂ eq) associated with Route A. Overall, its impacts vary from 1.47% (marine eutrophication) to 12.18% (ozone formation) of those associated with Route A across the different impact categories.

The decommissioning of offshore oil and gas (O&G) facilities poses significant challenges due to high costs, operational risks, social impacts, and environmental protection concerns. Multi-criteria decision analysis (MCDA) emerges as a vital tool to navigate these complexities, enabling stakeholders to evaluate diverse decommissioning alternatives against a broad set of criteria. Existing literature lacks extensive documentation on the application of MCDA in decommissioning decisions, particularly in quantitatively evaluating the performance of different decommissioning strategies against a comprehensive set of criteria. This study introduces a novel MCDA model tailored for the decommissioning of subsea O&G assets, aiming to improve decision-making by providing a quantitative ranking of decommissioning alternatives. Employing the Preference Ranking Organization Method for Enrichment Evaluations method, the model considers 37 attributes across six criteria (safety, environment, waste management, technical, social, and economic) to evaluate several decommissioning alternatives for the Brazilian Espadarte Field. Weightings and scenarios are defined through expert consultation, enhancing the model’s adaptability and relevance to real-world contexts. The model’s application demonstrated significant efficacy, with the selected top-ranked decommissioning alternative achieving a performance indicator of 58%, corresponding to the removal of 50% of the pipeline length considered. This result underscores the model’s capacity to identify optimal compromises between competing criteria. The study contributes to the field by filling the gap in the quantitative evaluation of decommissioning alternatives, offering a robust, transparent decision-making tool that accommodates complex, multi-criteria decisions. The model provides a significant advancement in the rationalization of decommissioning strategies for O&G assets.

The article aims to propose a social impact assessment model that can help operators in the oil and gas exploration and production sector to evaluate the social impacts in the onshore and offshore dimensions of the decommissioning of subsea oil and gas production systems. Based on the technical characteristics of the operation, the literature review and the workshops held with interested parties, the conceptual model was developed. The model includes 2 dimensions: (i) onshore, which encompasses impacts on logistics and infrastructure and onshore employability, and (ii) offshore, which involves external context, restrictions on artisanal fishing, restrictions on tourist activities and offshore employability. The impacts in both dimensions result from the operationalization of decommissioning. The contribution of this study is to propose a social impact assessment model that takes into account the onshore and offshore dimensions of the offshore-based decommissioning process of submarine systems and to propose future research. The proposed model can support decision-making by companies and governments in the process of decommissioning submarine systems and can also help other types of offshore installations.

Operators of offshore production units (OPUs) employ risk-based assessment (RBA) techniques in order to minimise inspection expenses while maintaining risks at an acceptable level. However, when human divers and workers are involved in inspections conducted at high heights, the operational risks can be significant. Recently, there has been a growing trend towards the use of unmanned aerial vehicles (UAVs), autonomous surface vehicles (ASVs), remotely operated vehicles (ROVs), and autonomous underwater vehicles (AUVs) for inspections of offshore structures as a means to reduce exposure to human risk. This article provides an analysis of these vehicle inspection capabilities and their potential to enhance robustness and safety within the oil and gas industry. The review assesses both the advantages and the drawbacks associated with these innovative systems, providing valuable comparisons and assessments on their potential use as viable alternatives to conventional inspection methods.

This article presents an experimental test program and numerical analyses conducted on aluminum alloy drill pipes with two different geometries. Small-scale characterization tests were conducted to determine both the material mechanical properties and the fatigue S–N curves. Full-scale fatigue tests of the components are also presented. A finite element model of the drill pipes, including the tool-joint region, was developed. The model simulates, through different load steps, the tool-joint hot-assembly and the experimental loads to obtain the actual stress distribution during the full-scale tests. Maximum stress amplitude in the aluminum pipes was found to be coincident with the edge of the connector, at the same location where failure was observed in full-scale tests. The study revealed that such pipes present a complex stress state near their connection to the steel tool-joints due to their geometry and the residual stresses induced during the assembly of the steel connectors onto the aluminum pipes. Finally, multi-axial fatigue models were calibrated with the results of the small-scale tests and applied to the stress–strain state obtained numerically. Theoretical predictions were correlated with full-scale fatigue test results.