Environmental Assessment of Brent North Sea Decommissioning: A Detailed Case Study
Authors: Maitra Sthitadhi , L Pachbiye Pranjal , Chauhan Geetanjali 
Published: April 2024

World's 70% of the hydrocarbon production occurs from mature oil and gas fields and many of such oil rigs and platforms in the world are nearing their "end of life" phase, and subsequent decommissioning and abandonment plans are being prepared. There is a necessity in the industry for early planning for the forecasted $100 billion global decommissioning activities of oil and gas facilities along with their associated midstream and downstream industries for risk management and cost optimization. Decommissioning in the offshore oil and gas industry involves the permanent closure and removal of facilities and infrastructure that are no longer economically viable or have reached the end of their operational life. This comprehensive process encompasses the cessation of production, plugging and abandoning wells, and the dismantling or removal of offshore platforms, pipelines, and associated structures. The process is highly regulated to ensure the safety of personnel, protect the environment, and comply with local and international regulations, reflecting the increasing importance of decommissioning as oil and gas fields globally age.

The decommissioning of offshore oil and gas facilities poses several technical, operational, social, economic and environmental challenges and it is imperative to address complicated and frequently costly process and also to minimize the damage caused to the environment. Lack of experience and difficulties in estimating liabilities and costs are major challenges in decommissioning and depending on the age, location, and compliance with safety and environmental standards of the facility, potential expenses could run into the billions of dollars. Assumptions about Cessation of Production (CoP), timelines for decommissioning operations, procedural elements, and inflation accounting are all part of the estimation process for decommissioning costs. Liabilities associated with decommissioning are complex, impacted by laws, regulations, contractual terms, and public perception. Other difficulties include ensuring sufficient financial assurance to finish projects and controlling safety and environmental risks during decommissioning. Since operators usually receive little to no revenue from decommissioning projects, obtaining adequate funding becomes essential to the successful completion of decommissioning operations.

Decommissioning can cause a disturbance of habitat during the removal of platforms, pipelines and subsea equipment. Residual hydrocarbons, heavy metals, and other chemicals may be present in the decommissioned infrastructure. Noise and vibrations during the decommissioning activities can affect marine mammals and fish. During decommissioning a large amount of waste materials and loose are produced. The disposal of decommissioned materials, including steel structures, concrete, and other materials, needs to be carefully managed to avoid negative environmental impacts. Decommissioning activities, such as the cutting and handling of pipelines and other equipment, also carry the risk of accidental oil or chemical spills. Thus, during Decommissioning Hazard (DEHAZ) study, it is imperative to identify and account for the waste generated during the operation and how it is disposed (Shaw,1994). The goal is to ensure that decommissioning activities are carried out in an environmentally responsible manner, minimizing harm to marine ecosystems and maintaining overall environmental sustainability.