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<p>This study uses petrophysical well-log data to characterize shallow aquifers and evaluate seal integrity in existing abandoned wells. In Brunei Darussalam, numerous abandoned onshore wells raise concerns about methane leakage from subsurface hydrocarbons and gas pockets, potentially leading to groundwater contamination and increased atmospheric methane emissions. Addressing these risks requires the integration of petrophysical well-log analysis using empirical data derived from gamma-ray, sonic, density, and resistivity logs. These datasets were interpreted to estimate key aquifer parameters, including porosity, permeability, lithology, and unconfined compressive strength (UCS) of shale. In addition, a multi-well correlation was applied to assess lateral continuity and variability of aquifer and seal units. Obtained porosity values (0.34–0.42) and permeability estimates (1900–3500 mD) indicate high-quality aquifers, while shale intervals showed low unconfined compressive strength (4.24–8.33&#xa0;MPa), reflecting weak seal integrity. A shallow gas pocket identified at depths of approximately 70–100&#xa0;m highlights potential methane migration pathways. The results provide insight into aquifer quality and the effectiveness of shale layers as potential seals against methane migration risks as well as supporting groundwater protection strategies in decommissioned hydrocarbon fields.</p>

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Well-log analysis for shallow aquifer characterization and seal integrity assessment in the Seria Field, Brunei Darussalam

  • 期刊论文

  • 发表日期：

    2026年6月26日

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  • A. D. Selavisi,
  • L. N. Osli,
  • B. Busahmin,
  • S. H. Gödeke

摘要

This study uses petrophysical well-log data to characterize shallow aquifers and evaluate seal integrity in existing abandoned wells. In Brunei Darussalam, numerous abandoned onshore wells raise concerns about methane leakage from subsurface hydrocarbons and gas pockets, potentially leading to groundwater contamination and increased atmospheric methane emissions. Addressing these risks requires the integration of petrophysical well-log analysis using empirical data derived from gamma-ray, sonic, density, and resistivity logs. These datasets were interpreted to estimate key aquifer parameters, including porosity, permeability, lithology, and unconfined compressive strength (UCS) of shale. In addition, a multi-well correlation was applied to assess lateral continuity and variability of aquifer and seal units. Obtained porosity values (0.34–0.42) and permeability estimates (1900–3500 mD) indicate high-quality aquifers, while shale intervals showed low unconfined compressive strength (4.24–8.33 MPa), reflecting weak seal integrity. A shallow gas pocket identified at depths of approximately 70–100 m highlights potential methane migration pathways. The results provide insight into aquifer quality and the effectiveness of shale layers as potential seals against methane migration risks as well as supporting groundwater protection strategies in decommissioned hydrocarbon fields.