overview of possible impacts from coal seam gas
development in Northern Rivers, New South Wales
Project by Elfian Schieren, 2012
5.4 Impacts on seismic activity
There is some concern from the community that drilling and
fraccing activities can potentially cause earthquakes of a magnitude that may
endanger lives and infrastructure.
The process of drilling and injecting and extracting fluids
into bedrock can change the existing stress state in the rock and cause seismic
activity to occur (Styles, 2012).
A phenomenon known as borehole breakout and drilling induced
fracture can occur when the removal of rock material within the borehole causes
the stresses in the surrounding rock to cause compressive or tensile failure in
the bore wall (Figure 6) (Asquith and Krygowski, 2004).
Usually these seismic events are localised and very small only
detectable with seismic testing equipment. Sometimes the stress spreads further
and moderate size tremors can be felt at the surface by people living nearby.
CSG engineers try to alleviate the chance of this happening by computer
simulation of rock stress, fracture behaviour and seismic activity (Beck, no
According to British media the mining company Cuadrilla admitted to being
the most likely cause for two earthquakes of 2.4 and 1.5 relative magnitude in
Blackpool in April, 2012 (White, 2012).
Further research confirmed that
hydraulic fracturing was in fact responsible for triggering the earthquakes in
Blackpool (Styles, 2012).
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