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Could Fracking Earthquakes Shake Pennsylvania?

  • Susan Phillips
Diagram of a deep well injection disposal site.

Adapted from the National Energy Technology Laboratory / Environmental Protection Agency

Diagram of a deep well injection disposal site.

Adapted from the National Energy Technology Laboratory / Environmental Protection Agency

Diagram of a deep well injection site.

The New Year’s Eve earthquake that shook Youngstown, Ohio measured 4.0 on the Richter scale. The temblor was the largest of a series of quakes that had been rocking the area around Youngstown for several months and are blamed on a deep injection well. No fracking happens at deep injection wells. But fracking wastewater is sent down those wells at high pressure as a method of disposal.
Researchers at Columbia University’s Lamont-Doherty Earth Observatory have studied the earthquakes in Ohio and identified the deep well they think caused the quake. The Youngstown well went into a sandstone formation, and then 300 feet further into more solid rock. John Armbruster, a seismologist with Lamont-Doherty, says the sandstone in that area is not very porous.
“The sandstone doesn’t want to accept this waste very easily,” says Armbruster. “So you have to use a lot of pressure to force the waste into the sandstone.”

When that pressurized fluid came in contact with a fault, the earth started to shake. Armbruster says it’s unlikely that the sandstone itself would have triggered a quake. But he says the Youngstown well was sunk deeper, into harder rock layers, where earthquakes were waiting to happen.
“The energy needs to be there,” says Armbruster.
In other words, it’s not just pumping large amounts of fluid down a hole into the earth. That fluid has to awaken a sleeping fault. Armbruster says it’s hard to know where those faults lie.
“You can say an earthquake is more likely or less likely,” he says. But you can’t say an earthquake is going to happen or not going to happen. There isn’t earthquake prediction.”
But there are ways that hydrologists and geologists can assess risk factors. Armbruster says things to look at are depth — does the well go beyond the sediment level and into the more solid basement levels? Are there layers of sediment between the bottom of a well and the basement level that could absorb the extra pressure? The state of Ohio is updating their rules about deep injection wells after the Youngstown quakes.
Pennsylvania’s wells, however, are regulated by the Environmental Protection Agency. Currently there are eight permitted injection wells in Pennsylvania. Injection wells are also called brine disposal wells, or class II underground injection wells. They can take any fluid related to oil and gas drilling. Two newly permitted wells in Warren County have not begun taking frack water yet, and are under appeal. EPA officials say they are looking at one new proposal. The EPA took over the task of permits, inspections and enforcement from state regulators in 1985. The map below shows where the wells are located. A click on the blue icon displays data on each brine water injection well.
Click blue icon to display pressure and volume data on each brine water injection well.
Unlike the Ohio wells, none of the Pennsylvania wells reach into the basement level formation. Scott Platt is an EPA hydrologist and an expert in underground injection control. Platt says the state’s injection wells are former gas and oil producing wells.
“We do not allow the well to operate at a pressure that would fracture a zone they go into,” says Platt.
Platt says the wells are in well known and well documented formations, so he says he feels comfortable with the permits.
Pennsylvania does have a history of earthquakes, but they’ve never been catastrophic. The U.S. Geological Survey’s Seismic Hazard Map for Pennsylvania shows a relative low probability that the state would experience an earthquake in the next 50 years. But it’s not much different than Ohio’s map.
Seismologist John Armbruster says it’s not just injection wells that can create earthquakes. Production work at quarries and oil fields can also shake loose unknown faults. He says a 1994 earthquake in Reading, Pa., measured more than a magnitude 4 on the Richter scale and centered right below a quarry.
But can fracking itself cause earthquakes? Armbruster doesn’t think so.
“Fracking wells tend to be shallow and it takes a day or two [to complete],” says Armbruster. That’s not enough pressure into these faults in the basement to make an earthquake.”
But once a quake does happen, Armbruster says the damage is done. The Ohio well injection company D & L Energy Group, has been ordered to pour cement into the bottom of the offending well.
“They pumped into that well for at least a year,” says Armbruster. “That’s not going away overnight. That effect will spread out for at least several months.”
In fact, the earthquakes that struck Youngstown, Ohio are not that far from a deep injection well in Beaver County. But the EPA says the Beaver County well does not extend beyond the sandstone layer. Three of Pennsylvania’s deep injection wells are commercial, which means they can take water from any energy company. The others are permitted only to dispose of their own frack water. Range Resources has an injection well in Erie County, which is permitted to take the most frack water in the state at 45,000 barrels per month. Some take as low as 4200 barrels per month, but most of them can take about 30,000 barrels a month. EXCO Resources operates two in Clearfield County. Other operators include Columbia Gas, in Beaver County; and Cottonwood and CNX Gas in Somerset. When it comes to pressure, the wells are permitted to take between 1300 to about 3200 pounds per square inch. If approved, the two newest wells will be operated by Bear Lake Properties in Warren County. All eight wells are in the western part of the state.
The oil and gas industry uses injection wells to dispose of waste water, which has a high salt content, as well as chemicals and heavy metals. Much of the frack water produced in Pennsylvania gets trucked to Ohio, which has more disposal wells. Water can also be treated at private treatment facilities. The process cleans most of the water, but at least some smaller amount of fluid still needs to be injected back into the ground.
Ohio is not the only state experiencing gas related earthquakes. Arkansas regulators banned the use of deep injection wells to dispose of wastewater after they found the activity caused a rise in small earthquakes last winter. The Arkansas Geological Survey told the AP last July that seismic activity decreased dramatically once the wells were shut down. The Arkansas Oil and Gas Commission has not banned fracking, only the use of wells to dispose of wastewater.
More than 40 years ago, a study conducted by the U.S. Geological Survey attributed a 5.3 magnitude earthquake in 1967 to a large injection well at the Rocky Mountain Arsenal in Denver, Colorado. Several smaller earthquakes followed the larger one.
A more recent study by Southern Methodist University and the University of Texas also linked a rash of small earthquakes in the Dallas-Fort Worth area in 2008 and 2009 to deep injection wells used to dispose of natural gas wastewater. But as the study’s authors pointed out, many similar wells operated in areas where no seismic activity occurred.
The Army Corps of Engineers has expressed concern about drilling for natural gas near dams and has a national team studying the potential impact. The Corps has requested a 3000 foot buffer around dams because it worries that fracking near fault lines could cause earthquakes or shifts in sediment that would weaken dam structures. CBS 11 News in Dallas reports that the Corp’s Fort Worth district wrote a letter in September to town officials in Grand Prairie, Texas warning them that a nearby Chesapeake Energy gas well site could potentially cause a “catastrophic dam failure.”

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