Oral Presentation Society of Environmental Toxicology and Chemistry Australasia 2021

Assessing the ecological risk of naturally occurring radioactive materials from subsea oil and gas infrastructure (#81)

Darren Koppel 1 , Stuart Higgins 1 , Amy MacIntosh 2 , Tom Cresswell 2 , Fenny Kho 1 , Dean Crouch 1 , Astley Hastings 3
  1. Curtin University Oil and Gas Innovation Centre, Bentley, Perth, WA, Australia
  2. Australian Nuclear Science and Technology Organisation, Lucas Heights, New South Wales, Australia
  3. National Decommissioning Centre, Newburgh, Scotland

Over 2500 offshore oil and gas structures will cease operations by 2040 globally and will require decommissioning at a cost of up to US$13 billion per year. In Australian waters alone, there is an estimated 8160 km of oil and gas pipelines of various sizes. In-situ decommissioning, where some infrastructure is left in the marine environment following the end of its productive life, has been promoted as an option that delivers net benefits, including: ecological benefits from the establishment of artificial reefs, reduced costs, and improved human safety outcomes for operators. However, lingering community and regulator concerns about potential negative impacts, such as the ecological risk of residual contaminants, are yet to be answered.

Naturally occurring radioactive materials (NORMs) are a class of contaminants found in oil and gas reservoirs that includes radionuclides of radium, radon, lead, and polonium. They can be concentrated in contamination products such as scales and sludges found in subsea oil and gas pipelines at activities >10,000 Bq/g. Despite this, their ecological risk to marine ecosystems is not well understood.

This presentation discusses an ecological risk-based framework to assess the risk of NORM contaminants in subsea oil and gas pipelines. A conceptual model of exposure pathways based on the expected environmental behaviour of the radionuclides is presented. Key environmental transformations and processes such as 210Po leaching, 222Rn emanation, and the reductive dissolution of RaSO4 minerals, are highlighted as key factors driving radionuclide mobility. Dosimetry modelling is also presented to demonstrate how environmental factors such as temperature and sediment quality affect ecological risk.

  1. MacIntosh, A., et al., 2021. Ecotoxicological effects of decommissioning offshore petroleum infrastructure: A systematic review. Critical Reviews in Environmental Science and Technology. 1-39.
  2. Advisian Pty Ltd., Offshore Oil and Gas Decommissioning Liability (Australia): Executive Summary. National Energy Resources Australia, Perth, Australia, 2020, pp. 9.