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Managing Contaminants During FPSO Decommissioning: Strategies and Considerations for BE&R Consulting

In the world of offshore oil and gas, the decommissioning of facilities, particularly Floating Production Storage and Offloading (FPSO) units, is a complex process that requires careful planning and execution. One significant challenge that arises during FPSO decommissioning is the effective management of contaminants.

Contaminants such as mercury, Naturally Occurring Radioactive Materials (NORMs), and tank bottoms pose potential environmental and health risks if not handled appropriately. In this article we delve into some of the complexities of decontamination and decommissioning in the oil industry, focusing on the contaminants of concern and the strategies for their safe removal and disposal.

Contaminants of Concern

Mercury (Hg)

Mercury is a persistent issue in the oil industry, often present in hydrocarbons at concentrations ranging from 1 to 100 nano-grams per kg of oil or m3 of gas (ηg/kg liquid or ηg/m3 gas). Some recent gas projects have even recorded significantly high concentrations exceeding 1100 ηg/m3.

Mercury absorption onto steel surfaces, including pipelines, vessels, and storage tanks, accumulates over the lifespan of a field. During decommissioning activities involving metal heating processes like angle grinding, hot-cutting, or welding, toxic mercury vapor can be released. Additionally, abandoning subsea pipelines raises concerns about the long-term impact of corroding pipes on oceanic mercury levels.

NORMs (Naturally Occurring Radioactive Materials)

Although produced fluids typically contain trace concentrations of radioactive elements like radium, strontium, and cesium, the levels are usually low and of minimal concern during production operations. However, during decommissioning, there is a risk of workers being exposed to radioactive dust when dismantling tanks, which can lead to health concerns.

Tank Bottoms:

The sludge and heavy hydrocarbons that accumulate at the bottoms of FPSO tanks can be challenging to manage. FPSO tanks may contain up to two meters of this viscous material, requiring solvents and/or steam for mobilization.

Decontamination Methods

The primary decisions in addressing contaminants during FPSO decommissioning revolve around whether to decontaminate in situ or relocate the facility to a specialist location. Decontaminating mercury adsorbed onto metal surfaces is a subject of ongoing research, especially concerning pipelines’ treatment before abandonment. Chemical washing is a commonly considered method for removing mercury from metal surfaces.

This process typically involves the use of chemical solutions or reagents that can bind to and remove mercury from the contaminated surfaces. Various types of chelating agents, such as EDTA (Ethylenediaminetetraacetic acid) and thiourea, have been investigated for their ability to complex with mercury and facilitate its removal from metal substrates. Specialist shipyards and piping fabrication yards may employ vacuum and fume recovery systems to protect workers and the environment during decontamination activities.

Disposal Routes

Mercury on absorbents can be recovered by specialized processors, potentially being converted into e.g. a pure liquid for sale as a commodity. Alternatively, it can be disposed of in registered landfills in a stable and insoluble chemical form.

NORMs can not be neutralized like toxic chemicals. Safe disposal options for materials emitting radiation levels above background include injecting them into wells as part of abandonment activities, sending them to registered landfills, or encasing them in concrete.

Tank bottoms often find their way to refineries equipped with processes to transform them into marketable products such as bitumen, lube oils, or cosmetics. In some cases, they are used in road sealing materials, albeit with the drawback of producing slippery roads until breakdown occurs under UV light.


Managing contaminants during FPSO decommissioning is a complex and costly endeavour. Contaminants in this context can refer to a wide range of substances, such as hazardous materials, pollutants, and waste products that need to be properly handled and mitigated to minimize environmental harm and ensure worker safety. These contaminants can significantly increase the overall cost of the decommissioning process, with labour costs being a major contributing factor. Here’s an expanded discussion on these cost components:

  1. Environmental Impact Assessment (EIA): Conducting a comprehensive EIA is essential to identify potential environmental risks and impacts associated with the decommissioning process. This involves studies, data collection, and assessments carried out by environmental experts.
  2. Labour Costs: Managing contaminants during FPSO decommissioning is a labour-intensive task. Skilled workers are required to handle hazardous materials, operate decontamination equipment, and ensure proper waste segregation and packaging. Labor costs can be two to three times higher than conventional decommissioning due to the specialized expertise and safety precautions involved.
  3. Safety Equipment and Gear: Workers involved in managing contaminants must wear specialized safety gear and equipment to protect themselves from exposure to hazardous substances. This includes respirators, protective suits, gloves, and other safety equipment.
  4. Regulatory Compliance Costs: FPSO decommissioning must adhere to strict regulatory guidelines and standards. Ensuring compliance with these regulations requires resources and investments in documentation, reporting, and adherence to safety protocols.
  5. Waste Segregation and Packaging: Proper segregation and packaging of waste materials are crucial to prevent cross-contamination and ensure safe disposal. This involves the use of specialized containers and labelling.
  6. Decontamination Equipment: Specialized equipment is necessary for decontaminating equipment, machinery, and facilities used in the decommissioning process. This equipment must meet stringent safety and environmental standards, adding to the cost.
  7. Monitoring and Testing Equipment: Continuous monitoring and testing of the environment and personnel are necessary to ensure safety and compliance. The procurement and maintenance of monitoring and testing equipment contribute to project expenses.
  8. Transportation Logistics: Contaminated materials must be transported safely and securely to designated disposal sites. This includes arranging for specialized transportation methods and logistics.
  9. Disposal Site Fees: Fees associated with the disposal of hazardous waste at authorized facilities can be substantial, especially when dealing with contaminants from FPSO decommissioning.
  10. Contaminant Remediation: Remediation efforts may be required to mitigate the long-term environmental impact of contaminants. These efforts involve additional costs for cleanup and restoration potentially well past the life of the initial decommissioning project.
  11. Environmental Consultants: Engaging environmental consultants and experts to provide guidance, assessments, and expertise throughout the decommissioning process is necessary.
  12. Waste Tracking and Documentation: Comprehensive tracking and documentation of waste generation, handling, and disposal are essential for regulatory compliance. Maintaining accurate records is both time-consuming and costly.
  13. Public Relations and Community Engagement: Engaging with local communities and stakeholders to maintain transparency and address concerns is vital. Public relations efforts may require additional services for promotions, lobbying and advertising.
  14. Legal Costs: Legal assistance may be required for navigating complex regulations, obtaining permits, and addressing any potential disputes or liabilities that may arise during decommissioning.
  15. Planning and Approvals: Effective planning and obtaining necessary approvals, as mentioned, involve costs related to regulatory submissions, consultations, and negotiations with relevant authorities and stakeholders.

In summary, managing contaminants during FPSO decommissioning is a complicated and expensive process due to the need for specialized labour, equipment, compliance with stringent regulations, and the complex nature of handling hazardous materials.

Effective planning, budgeting, and adherence to environmental and safety standards are essential to successfully complete such projects while minimizing environmental impact and ensuring safety. Good practice would include benchmarking your costs estimates against similar projects.


The management of contaminants during FPSO decommissioning is a multifaceted challenge that demands thorough planning, adherence to regulatory requirements, and a commitment to environmental stewardship. BE&R Consulting recognizes the importance of addressing this issue with diligence and professionalism.

By comprehensively managing contaminants and adhering to best practices, we can contribute to environmentally responsible decommissioning practices and bolster our reputation in the industry.


Decommissioning Research Needs for Offshore Oil and Gas Infrastructure in Australia, https://www.frontiersin.org/articles/10.3389/fmars.2021.711151/full , 29 July 2021, Frontiers.


Northern Endeavour Phase 1 Decommissioning, https://epbcpublicportal.awe.gov.au/_entity/sharepointdocumentlocation/6a3d9448-7155-ed11-9562-00224818a1ee/2ab10dab-d681-4911-b881-cc99413f07b6?file=Att%201-EPBC%20Referral%20Supporting%20Document-V2-2022-10-17.pdf , 17 October 2022, GHD & The Department of Agriculture, Water and the Environment.