Fracking Quakes Shake the Shale Gas Industry
January 20, 2012
Geophysicists are increasingly certain that expanding production of shale gas is responsible for a spate of minor earthquakes that have upset some communities and prompted authorities in Arkansas, Ohio, Oklahoma, and the U.K. to shut down some natural-gas operations.
McGarr at USGS says an early warning system is a good idea, and one in keeping with the seismic risk assessment protocol for well-blasting operations employed by geothermal-energy producers. He is less sanguine, however, about estimates of the maximum severity that earthquakes triggered by fracking and injection wells can reach, saying this question needs more science. That means the risk of anthropogenically inducing large, deadly quakes cannot be ruled out.
Fracking Byproducts May Be Linked To Ohio Quakes
January 3, 2012
A series of earthquakes that have shaken Ohio over the last year were most likely caused by the injection deep underground of wastewater generated by drilling. That's the conclusion of a seismologist who's been studying the quakes and their connection to deep-injection disposal wells.
Youngstown is an area which doesn't have a history of earthquakes. This disposal well started operating in December of 2010. Three months later, the earthquakes began and the earthquakes are trickling along. From March to November, you have nine earthquakes, all of a similar size, 2.5, 2.1, 2.7.
Our location of that Christmas Eve earthquake was about one kilometer from the bottom of the well and the location of the earthquake was sufficient evidence that there could be a link.
A statement from an industry group says that these kinds of wells have been used safely and reliably since the 1930s to dispose of waste water from drilling.
Ohio Earthquake Likely Caused by Fracking Wastewater
January 4, 2012
The fluids can act as lubricants between two abutting rock faces, helping them to suddenly slip along the boundary.
The scientists did say that subsequent quakes from the Youngstown injections, which had been underway for a year, could continue to occur for up to another year, even if no more fluids are added.
Ohio lawmakers have asked Northstar to stop operations until a full investigation is complete; the company has agreed but is not talking publicly about the events.
How Fracking Wastewater Is Tied To Quakes
January 5, 2012
Some rock is saturated with water -- the water occupies pores between rock particles. This creates what's called "pore pressure" and keeps the formation in a sort of equilibrium. If you suck the water out, particles tend to collapse in on themselves: the rock compresses. Add water, and you push particles apart. So moving water around underground can affect the stresses on those formations.
Recent quakes reported in Ohio and Arkansas are associated with wastewater wells, not fracking wells. The water first used in fracturing rock is retrieved and pumped into these waste wells, which take in lots of water. And at more than 9,000 feet deep, the water is under high pressure that can build up over months or years. It's this pressure that can actually create earthquakes.
In the 1960s, a wastewater well in Colorado at the Rocky Mountain Arsenal is believed to have been the trigger for a magnitude-4.8 quake.
One way to avoid creating earthquakes is not to inject fracking wastewater into waste wells, but to recycle it instead.
The state of Pennsylvania tried that, but they found that wastewater treatment plants couldn't get all of the toxic material out of fracking water, and the "cleaned up" water returned to rivers wasn't clean enough. So well operators in the state decided to ship wastewater to Ohio, where it has been going down into wells.
The U.S. Geological Survey is working on ways to head off quakes from wastewater wells. That would include performing seismic surveys before drilling the wells. Permeable rock like sandstone is better than hard, brittle basement rock that is riddled with faults. Operators might also limit the amount of water going into wells: USGS geologists have learned that the more water injected, the bigger an ensuing quake.
Arkansas Earthquakes Decline After 'Fracking' Injection Well Closures
The Center for Earthquake Research and Information recorded around 100 earthquakes in the seven days preceding the shutdown earlier this month, including the largest quake to hit the state in 35 years -- a magnitude 4.7 on Feb. 27. A dozen of the quakes had magnitudes greater than 3.0.
In the days since the shutdown, there have been around 60 recorded quakes, with only one higher than a magnitude 3.0. The majority were between magnitudes 1.2 and 2.8.
The two injection wells are used to dispose of wastewater from natural-gas production. One is owned by Chesapeake Energy, and the other by Clarita Operating. They agreed March 4 to temporarily cease injection operations at the request of the Arkansas Oil and Gas Commission.
The commission said preliminary studies showed evidence potentially linking injection activities with nearly 1,000 quakes in the region over the past six months.
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