http://stateimpact.npr.org/texas/2012/08/06/how-fracking-disposal-wells-are-causing-earthquakes-in-dallas-fort-worth/
If you live in the Barnett Shale around Dallas-Fort Worth, Texas, you may have noticed the ground has become a bit shakier in the last few years. And a new study by a Univeristy of Texas seismologist says that the wells used to dispose of fracking waste water are responsible. What’s more, there have been more than eight times as many earthquakes in the area than previously thought.
The rapid expanse of hydraulic fracturing, or “fracking,” has also led to an increase in the number of wells needed to dispose of the water used in the drilling process. (Fracking is a drilling process that uses a mixture of water, sand and chemicals to fracture rock formations deep underground for oil and gas.) Once that waste water comes back up the well, it has to be disposed of, so drillers inject it into deep wells underground, as deep as 13,000 feet below the surface in the Barnett Shale.
The problem, according to the new study by Dr. Cliff Frohlich, senior research scientist at the University’s Institute for Geophysics, is that some of those disposal wells around Dallas-Fort Worth are also on fault lines.
The seismologist uses the analogy of an air hockey table to describe what’s going on. If the air is turned off, the puck won’t move even if you push it. But when you pump in the air, it moves easily. With disposal wells sending fracking waste water deep underground, liquid and pressure are migrating into a “stuck” fault. “It wants to move but it can’t,” Frohlich tells StateImpact Texas. “Until you pump fluids in there and it slips.” Over 6 millions gallons of fracking waste water a month was pumped into each of the wells near the epicenters examined in the study...
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