Understanding connectivity between coal seams and aquifers

Integrating geochemical modelling and airborne geophysical surveys to refine the understanding of connectivity between coal seams and overlying aquifers

This project will further improve our knowledge of groundwater systems in the Gunnedah and Surat Basins in the Narrabri region and refine the conceptual understanding of potential for hydrogeological connectivity pathways between shallow aquifers.

CSIRO’s previous research into these groundwater systems has generated important knowledge on the nature of these systems and potential for connectivity between primary target seams for coal seam gas (CSG) development and agricultural aquifers.

The agriculturally important Pilliga Sandstone and other alluvial aquifers are separated from the deeper Gunnedah Basin formations (which include the CSG target units) by aquitards which range in thickness from 300 metres to 700 metres. Aquitards are compacted layers of clay, silt or rock that act as a barrier for groundwater movement.

This research adopts a multi-disciplinary approach that combines existing data with targeted acquisition of new hydrochemistry, geochemistry, and geophysical survey data.

The outcome of this project will include the generation of high-resolution 3D realizations of the subsurface that represent continuous geological structures.

This will provide additional information on the potential for connectivity pathways between the CSG target units and adjacent groundwater systems, and reduce uncertainty about the potential drawdown at depth impacting on aquifer pressure in the confined Pilliga Sandstone aquifer and adjacent alluvium.

Above: CSIRO researchers conducting a ground-based electromagnetic survey in the Narrabri region in 2021. In late 2023 CSIRO will use a helicopter to conduct an airborne electromagnetic (AEM) survey in the Narrabri region as part of this current research (see below).