The Beetaloo GBA region is prospectivefor unconventional gas and is estimated to contain significant technically recoverable unconventional gas resources. To date, there has been limited exploration, with exploration permits currently operated by Origin Energy, Santos and Pangaea Resources ( Figure 2 ). Empire Energy Group Limited entered a binding Sale and Purchase Agreement with Pangaea (NT) Pty Ltdto acquire Pangaea’sBeetaloo Sub-basin tenements in April 2021, with the acquisition due to be completed in mid-2021. Hall et al. (2020) present the 5 identified unconventional petroleum plays in the Beetaloo GBA region most likely to be developed within the next 5 to 10 years (after Côté et al. (2018), Figure 4 ):
- Velkerri Shale (Amungee Member) – dry gas play
- Velkerri Shale (Amungee Member) – liquids-rich gas play
- Kyalla Shale – liquids-rich gas play
- Kyalla Hybrid Lithology – liquids-rich gas play
- Hayfield sandstone member – tight oil/condensate play.
Of these plays, there are only sufficient public domain data available to independently assess the dry and liquids-rich gas plays of the Amungee Member shales of the Velkerri Formation, and the liquids-rich gas in the Kyalla Formation shale.
The current conceptual hydrogeological model forthe Beetaloo GBA region consists of 3 individual groundwater subsystems underlain by the Roper Group (the sedimentary package that is host to primary unconventional gas plays of the Velkerriand Kyalla formations). From oldest to youngest, the conceptual model comprises the following components:
- Neoproterozoic rocks and overlying Cambrian Antrim Plateau Volcanics (confined aquifer throughout most of the region)
- Cambrian Limestone Aquifer system (consisting of an upper and lower aquifer sequence) (unconfined aquifer throughout most of the region)
- Undifferentiated Cretaceous Carpentaria Basin and Cenozoic sedimentary rocks (generally unsaturated) (unconfined aquifer).
The Cambrian Limestone Aquifer is the most significant aquifer in the region (in terms of both spatial coverage and use). The deeper, Neoproterozoic fractured rocks also contain aquifers within the Beetaloo GBA region, including the Bukalara and Jamison sandstones. Limited supplies of groundwater are also sourced from the aquifers of the Cretaceous Carpentaria Basin and Cenozoic sediments.
Relative prospectivity determines the relative likelihood of a resource (e.g. oil, gas, groundwater) through analysis of geological properties (e.g. formation depth and extent, rock properties, reservoir characteristics).
Data: Northern Territory Geological Survey (2020) Element: GBA-BEE-3-551
FIGURE 3 Surface and shallow groundwater features of the Beetaloo GBA region
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This schematic diagram is not drawn to scale.
Element: GBA-BEE-3-571
FIGURE 4 Conceptual cross-section of the Beetaloo GBA region
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The stratigraphy varies across the region. Formation thicknesses and fracture heights are indicative only. Not to scale, for illustrative purposes only. Potential stressors are indicated.
Element: GBA-BEE-3-572
