SEP 13, 2016 8:46 AM PDT

What does fracking have to do with Oklahoma's earthquakes?


A magnitude 5.6 earthquake shook Oklahoma on Saturday, making it tied for the strongest quake ever recorded in the state. The quake was most likely triggered by fracking operations, particularly the subsurface injection of fracking wastewater and produced waters in general, including those from non-fracking operations.
 

In fracking, people use pressurized water mixed with sand and additive chemicals to crack open small fissures in the rock and release trapped hydrocarbons. In conventional oil and gas extraction, water is often trapped alongside the resources we want and comes up with them — contaminated by those resources. The water is no longer potable, so companies try to inject it down below the water table. There are more than 10,000 wastewater injection wells in Oklahoma — and the state’s 2015 earthquakes cluster right on top of some of the wells, which are on top of some of the faults.

The earthquakes seem to be a result of the injection of fracking wastewater and other waste and production water, even from non-fracking wells, at depths well-below the fracking horizon. The larger the volumes of water injected into the subsurface, the larger the earthquakes can be.
 
Oklahoma Corporation Commission, Oklahoma Geological Survey
 
In fracking, people use pressurized water mixed with sand and additive chemicals to crack open small fissures in the rock and release trapped hydrocarbons. In conventional oil and gas extraction, water is often trapped alongside the resources we want and comes up with them — contaminated by those resources. The water is no longer potable, so companies try to inject it down below the water table. There are more than 10,000 wastewater injection wells in Oklahoma — and the state’s 2015 earthquakes cluster right on top of some of the wells, which are on top of some of the faults. The following is cut from a 60 Minutes interview:

“Mark Zoback: What we’ve learned in Oklahoma is that the earthquakes that are occurring in enormous numbers are the result of wastewater injection.

Mark Zoback is professor of geophysics at Stanford University. Zoback says there are two factors behind the earthquakes. One is the large volumes of water being disposed and the other is where it all goes: deep down into a layer of earth called the Arbuckle.

Bill Whitaker: What makes this such a good place to dispose of all that water?

Mark Zoback: Well, it’s very thick. It’s porous, it’s permeable so it can accommodate, you know, very large injection rates.

The only problem with the Arbuckle is that it sits directly on top of the crystalline basement -- a rock layer riddled with earthquake faults.

Bill Whitaker: So this water is seeping into the faults?

Mark Zoback: The water pressure is seeping into the faults. And the fault is clamped shut and the water pressure sorta pushes the two sides of the fault apart and allows the slippage to occur today, when it might not occur for thousands of years into the future.”

Sources: Forbes, Zero Hedge, Five Thirty Eight, CBS News
About the Author
BA Environmental Studies
Kathryn is a curious world-traveller interested in the intersection between nature, culture, history, and people. She has worked for environmental education non-profits and is a Spanish/English interpreter.
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