Wednesday, March 27, 2013

Water injection induced quake, says study

With all the environment concerns around fracking, a new study may just be sounding another alarm. It says that wastewater injection was the major trigger for the Prague earthquake of 2011.

Wastewater injection is the removal of water from fossil-fuel energy production into the ground — whether for hydrofracking, which uses the pressure of the water to crack open rocks to release natural gasses, or using the water to force petroleum out of conventional oil wells. In both cases the water has to be disposed of somewhere away from drinkable and habitable water supplies, so it is often pumped underground somewhere.

Geologically sedate areas of Arkansas, Texas, Ohio, and Colorado have recently become relatively earthquake-prone, with quakes in the middle of the US jumping 11-fold over the past four years when compared to the previous three decades. The risk is such that the National Academy of Sciences in a report last year called for further research to “understand, limit and respond” to induced seismic events.

The present study looked at the evidence for the Prague quake November 6, 2011, when a 5.7 magnitude and found that as wastewater refilled now-empty oil wells the pressure to continue filling the holes with water had to be increased which caused the Wilzetta fault to jump. The amount of wastewater injected into the well was relatively small, yet it triggered a cascading series of tremors that led to the main shock, said study

The study’s authors believe that water injection should be kept away from known fault locations, and that companies involved in wastewater injection should be compelled to provide accurate measurements of the amount of water that is being pumped into the ground and at what pressure. They also recommend that sub-surface monitoring of fluid pressure for earthquake warning signs.

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