Fracking and Earth quakes: listing the facts
Reporter: Geert deCock – Food and Water EUROPE
My colleagues in the US listed some helpful facts about fracking, shale gas and induced seismicity
There is now a lot of talk about this, as scientists now linked fracking waste water injection to a surge of quite big earth quakes in Oklahoma. See this Reuters article.
The industry and its affiliates would like to dismiss the fact that many new earthquakes sweeping across the nation are fracking-related.
Hydraulic fracturing itself can cause earthquakes, they just tend to be smaller and less frequently felt than earthquakes produced from underground injection control wells
I n 2011, fracking was associated with a 3.8 magnitude earthquake in British Columbia, Canada
In 2011, in Blackpool, England, two earthquakes were directly linked hydraulic fracturing
Fracking has also been linked to a “felt” earthquake in Garvin County, Oklahoma in 2011.
An Ohio-based study that came out in 2015 pinpointed fracking as the cause of a 3.0 magnitude earthquake near the Poland Township
In late 2014 a Seismological Research Letters study found that fracking is the likely culprit for hundreds of small tremors in Ohio
The public generally uses the term fracking to refer to the entire process, including drilling, blasting apart the rock formations, dealing with the wastewater and more. You cannot frack a well and not have wastewater flow back.
Underground injection control wells are a common method of disposal for fracking waste
In the eastern and central United States, earthquake activity has increased about fivefold, from an annual average of 21 earthquakes above a 3.0 magnitude between 1967 and 2000, to more than 300 earthquakes above a 3.0 magnitude over three years from 2010 to 2012
According to scientists with the U.S. Geological Survey (USGS), this increased seismic activity is associated with wastewater disposal wells in states such as Oklahoma, Colorado, Arkansas, Ohio and Texas
The threat of increased earthquake activity is of concern for the seismically active state of California, where the Monterey Shale overlaps the San Andreas Fault
Induced seismicity occurs when human activity triggers a dormant fault by adding or reducing stress and/or increasing pore pressure
Pore fluids are fluids that inhabit the pore space in a rock.
Fluid pumped underground can cause pressure in a rock’s pores or fissures; this pressure is known as fluid pressure or pore pressure.
Fluid can play a major role in controlling stress that is being applied to a fault; changes in pore pressure – such as an increase in fluids – can cause changes in the forces (tectonic forces, for example) holding a rock together.
This can cause an earthquake.
When fluid is injected underground — as is done to fracture shale rock and for the disposal of fracking wastewater — it can lubricate fault zones. As fluid moves into a fault zone, pore pressure increases, which can cause the fault to slip and result in an earthquake
Fluid pressure from high-rate disposal wells can migrate, so even if an injection well is not very close to a fault line or to one that is susceptible to earthquakes, the fluid pressure can migrate long distances to reach a fault that is more susceptible
Induced seismic events may not always strike soon after the injection activity begins. It may take a long time for an earthquake to trigger, and sometimes not until after the injection activity has ended
Food and water Europe