Browsing by Author "Apte, S"

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    Analysis of uranium, thorium and radium radioisotopes in coal seam gas associated water samples
    (South Pacific Environmental Radioactivity Association, 2018-11-06) Maizma, S; Chellappa, J; Zawadzki, A; Apte, S; King, J; Jarolimek, C; Angel, BM
    The Australian coal seam gas (CSG) industry, located mainly in eastern Australia, has grown significantly over the last decade and is now a significant contributor to natural gas production in Australia. CS6 extraction involves drilling boreholes across landscapes which intersect with coal seams. Gas is then flowed to the surface along with associated produced waters. In order to increase gas production, some wells are subjected to hydraulic fracturing which involves pumping water, chemicals and a proppant into the coal seams. The resulting flow-back waters are then collected at the surface prior to treatment and disposal. There are significant public concerns about the water quality of flow-back and produced waters associated with CSG operations, in particular the concentration of geogenic contaminants including radioisotopes such as 226Ra and 222Ra. In order to address these concerns, accurate data on water quality needs to be collected. CSG waste waters are complex, saline matrices and sensitive, robust analytical methods are required to reliably quantify the concentrations of contaminants including radioisotopes ln this work, radioisotopes of uranium, thorium and radium were analysed in CSG flow-back and produced waters samples collected from CSG bores located in Central Queensland, Australia. The water samples were processed for the determination of 233U, 238U, 228Th, 230Th, 232Th, 226Ra activity concentrations by alpha-particle spectrometry and 222Ra by gamma-ray spectrometry. GSG associated water consist of high concentrations of total dissolved solids (TDS) ranging from 800 to 10,000 mg/L. Such high salinity levels pose difficulties for the measurement of the radioisotopes of interest, resulting in low sample recoveries and poor resolution alpha spectra. This paper presents radiochemical techniques used to reduce the complex sample matrix effects in analysing CSG associated water samples. Manganese dioxide co-precipitation technique was chosen to concentrate the elements of interest, followed by the isolation of uranium and thorium using UTEVA (Eichrom) resin. The determination of 222Ra by alpha spectrometry was found to be challenging due to low sample recoveries and poor alpha spectra resolutions. This was overcome by diluting the samples in large volumes prior to lead sulphate co-precipitation, which isolates radium and barium from other metals in the samples. The developed radiochemical technique was suitable and robust for determining the radioisotopes of interest in CSG associated water samples.
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    Assessing the impacts of scale residues from offshore oil and gas decommissioning on marine organisms
    (CSIRO Publishing, 2021-07-02) Cresswell, T; Brown, S; Wong, HKY; Apte, S
    Successful decommissioning of offshore oil and gas infrastructure requires an effective and safe approach to assessing and managing chemical and radiological residues. Scale frequently accumulates on the interior surfaces of pipes and other structures and may persist long after extraction operations have ceased. Scale materials can contain a range of metal contaminants (including mercury), as well as naturally occurring radioactive materials. In newer or more accessible infrastructure, the scale is routinely removed, and becomes a waste product. The persistent nature of scale contaminants can result in a radiological dose to the organisms living on, or near an intact pipeline. Eventually, infrastructure corrosion following in situ decommissioning (abandonment) could lead to metal and radionuclide contaminants being accessible to the surrounding seafloor environment, where bioaccumulation and subsequent ecotoxicological effects from the chemical and radiological properties of the scale could occur. The paper describes a tiered approach to assess the ecological impacts of pipeline scale in order to assist operators with their plans for decommissioning offshore infrastructure, especially when considering ‘leave in place’ options. © CSIRO 2021
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    Assessing the risk of NORM scale to marine biota from offshore oil and gas decommissioning
    (International Atomic Energy Agency, 2020-10-19) Creswell, T; Apte, S; Wong, HKY; Brown, S
    Successful decommissioning of offshore oil and gas infrastructure requires an effective and safe approach to assessing and managing chemical and radiological residues. Scale residues frequently accumulate on the interior surfaces of pipes and other structures, and may persist long after extraction operations have ceased. Scale materials can consist of a range of metal contaminants (including mercury), as well as naturally occurring radioactive materials (NORM). In newer infrastructure, the scale is cleaned routinely, and becomes a waste product. The persistent nature of ‘NORM scale’ can result in a radiological dose to the organisms living on, or near an intact pipeline. Eventually, pipe corrosion could lead to metal and radionuclide contaminants being accessible to the surrounding benthic environment, where bioaccumulation and subsequent ecotoxicological effects from the chemical and radiological properties of the scale could occur. This presentation describes a multi-phase approach to assessing the ecological impacts of pipeline scale in order to assist operators with their plans for decommissioning offshore infrastructure. Recent results from pipeline scale testing will be discussed.
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    A review of the potential risks associated with mercury in subsea oil and gas pipelines in Australia
    (CSIRO, 2022-11-01) Gissi, F; Koppel, DJ; Boyd, A; Kho, F; von Hellfeld, R; Higgins, S; Apte, S; Cresswell, T
    In the coming years, the oil and gas industry will have a significant liability in decommissioning offshore infrastructure such as subsea pipelines. The policies around decommissioning vary depending on regional policies and laws. In Australia, the ‘base case’ for decommissioning is removal of all property and the plugging and abandonment of wells in line with the Offshore Petroleum and Greenhouse Gas Storage (OPGGS) Act 2006. Options other than complete removal may be considered where the titleholder can demonstrate that the alternative decommissioning activity delivers equal or better environmental outcomes compared to complete removal and meets all requirements under the OPGGS Act and regulations. Recent research has demonstrated that decommissioning in situ can have significant environmental benefits by forming artificial reefs, increasing marine biodiversity, and providing a potential fishery location. An issue, which has been given less attention, is around contaminants remaining within decommissioned infrastructure and their potential risks to the marine environment. Mercury is a contaminant of concern known to be present in some oil and gas pipelines, but the potential long-term impacts on marine ecosystems are poorly understood. We present a synthesis of information on mercury cycling in the marine environment including key drivers of methylation in sediments and ocean waters, existing models to predict methylmercury concentrations in sediments, and toxicological effects to marine biota. We discuss the applicability of existing water and sediment quality guidelines, and the associated risk assessment frameworks to decommissioning offshore infrastructure contaminated with mercury. Globally, research is needed to provide a comprehensive risk assessment framework for offshore infrastructure decommissioning. We recommend future areas of research to improve our understanding of the potential risks associated with mercury in subsea oil and gas pipelines. © 2022 The Author(s) (or their employer(s)). This is an open access article distributed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License (CC BY-NC-ND).