This short video presents a three dimensional
view of the geology in the Surat Cumulative
Management Area.
This geological information is used to inform
modelling processes.
The Surat Cumulative Management Area covers
extensive CSG development in the Surat, southern
Bowen and Clarence-Moreton Basins.
Located between Toowoomba and Mitchell in
the west and extending north from Goondiwindi
to Blackwater in central Queensland, the area
is approximately 400 kilometres wide and almost
600 kilometres long.
The Surat Basin contains a number of geological
formations layered on top of each other.
The various geological layers are exposed
in the northern and eastern part of the basin,
allowing surface water to penetrate.
From this recharge area, water moves south
or south-west.
Each formation is represented by a different
colour.
The compass in the upper right hand corner
shows the orientation of the image.
The blue line points up, while the green line
indicates north and the red east.
The Bowen Basin is deep, reaching more than
nine kilometres below the surface, and runs
in a north-south direction.
The depth and thickness of each formation
varies across the area.
The formations in the Surat Basin are generally
exposed at the surface in the north.
Aquifers, shown in blue, supply groundwater.
The aquitards, in orange, separate the aquifers
and restrict groundwater movement between
aquifers.
The coal seam gas producing formations are
shown in grey and the Condamine Alluvium,
in the upper right, is in yellow.
In the south, the Surat Basin overlies the
Bowen Basin, whilst to the north the Surat
Basin thins until it no longer exists.
As we move northwards, the younger sediments
of the Surat Basin thin and disappear, while
the older and deeper sediments eventually
reach the surface until only the formations
of the Bowen Basin exist.
The hydrogeology of the Surat, southern Bowen
and the Clarence-Moreton Basins is complex
– consisting of many alternating layers
of permeable sandstone aquifers and less permeable
siltstone and mudstone aquitards.
The area, thicknesses and hydraulic properties
of these layers are highly variable.
The Bandanna Formation is the target for coal
seam gas extraction in the Bowen Basin.
At its maximum depth, it is more than five
kilometres below the surface.
Note the geological formations do not fit
perfectly over each other, and the shallower
layers cover a wider area.
The small map in the lower left corner shows
the extent of the geological layer currently
being viewed.
The yellow line on this map is the Surat Cumulative
Management Area.
The Walloon Coal Measures is the target formation
for CSG production in the Surat Basin. Water
is pumped from this layer to release the gas.
There are geological formations above and
below the Walloon Coal Measures.
These formations are known as aquitards – in
this case, a shale layer of varying thickness.
The aquitards separate the underlying aquifer
and the overlying aquifer from the productive
coal seam layers.
The Condamine Alluvium has been deposited
by the Condamine River and its tributaries.
Many irrigators draw water from this alluvial
system.
These variations are just some of the challenges
that make the creation of a regional groundwater
flow model for a large area a complex exercise.
