This video presents the geology in the
Surat cumulative management area.
This 3D geological information is built by the Office of Groundwater Impact Assessment
for its groundwater impact assessment
from coal seam gas development in the
area. The Surat cumulative management
area contains a number of geological
formations layered on top of each other.
The Bowen Basin is the deepest reaching
more than 9 kilometres below the surface
at centre and runs north-south. The Surat
Basin sits on top of the Bowen Basin the
different geological formations that
comprise the Surat Basin are shown in
different colors here from bottom to top
and are listed in the legend to the left.
The Surat Basin is 2.5 kilometres deep
and spreads wider than the Bowen. The
Surat Basin is a mix of alternating
layers of sandstone, siltstone, mud stone
and coal. As we move south to north the
formations vary in depth and thickness.
One of those formations the balloon coal
measures is the target formation for
coal seam gas production in the Surat
Basin. Now you can see a north-south
cross section of the Surat and Bowen
basins. In the south the Surat Basin
overlies the Bowen Basin
whilst to the north the younger
sediments of the Surat Basin thin and
disappear. The older and deeper sediments
eventually reach the surface until only
the formations of the Bowen Basin are
exposed.
At the south eastern end the Condamine
alluvium is about 120 meters thick in
the central flood plain near Dalby and
sits on top of the Surat Basin and it's
equivalent the Clarence Morton Basin. In
the east the Walloon Coal measures lies
directly underneath it. Next to this is
the basalt layer of the main range volcanics.
There are a number of regional
geological faults in the Surat CMA.
Mainly deep-seated basement faults
primarily affect the Bowen sediments and
in some circumstances also affect the
Surat Basin. Displacement along the
faults is much less in the Surat Basin
compared to the Bowen Basin. All this
knowledge about the complex geology was
gathered in the generation of a 3D
geological model primarily built from
interpretation of wells and bores that
are drilled for exploration and
production. A technique called
geophysical logging is used to interpret
the depths of various sandstone mud
stone and coal layers. The Office of
Groundwater Impact Assessment has
primarily used logs from over 7,000
petroleum and gas wells and 25,000 water
bores to build the formation layering.
Geological mapping and seismic surveys
are also key datasets used for
geological modeling. The resulting model
forms the framework for impact assessment.
 
