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Groundwater Volume Estimation by Combining AEM, NMR and Petrophysical Data
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, Near Surface Geoscience 2015 - 21st European Meeting of Environmental and Engineering Geophysics, Sep 2015, Volume 2015, p.1 - 5
Abstract
Estimating groundwater storage volumes is important for assessing the potential capacity and recovery efficiencies of Managed Aquifer Recharge (MAR) strategies. However, such storage estimates are challenging, particularly in areas of poor data density. This challenge faced the Broken Hill Managed Aquifer Recharge (BHMAR) project tasked with assessing groundwater options in the Darling River floodplain, NSW, Australia. Within the ~7500 km2 area, 14 fresh groundwater zones were identified with AEM and a workflow was developed to estimate the groundwater volumes in these targets.
Pore fluid sampling from sonic core provided the opportunity to develop simple AEM conductivity thresholds to produce surrogate groundwater salinity maps for each AEM depth slice. Combining the AEM data with other project datasets such as downhole geophysics, detailed sonic-core logging and laboratory analyses facilitated the mapping of hydrostratigraphy, textural classes and saturation within AEM depth slices, which were then used to calculate bulk aquifer volumes. Nuclear magnetic resonance (NMR) free-water statistics were used in effective porosity estimates, to calculate groundwater volumes.
Although preliminary, the volume estimates were essential in the identifying, prioritising, interpreting and reporting of groundwater resource targets during the project and to make recommendations for future phases of investigation.