Earthquake shakes up another North Texas town

By Kathryn Jones

Editor

Another North Texas earthquake – this one on Sunday in Benbrook southwest of Fort Worth – is raising more questions about the possible relation between seismic activity and natural gas and oil drilling.

Energy industry officials insist that fracking by Barnett Shale rigs is safe.

Energy industry officials insist that fracking by Barnett Shale rigs is safe.

The U.S. Geological Survey reported a 2.3 magnitude earthquake rattled Benbrook at 1:32 p.m. Sunday. The epicenter was east of Benbrook Lake and west of Granbury Road. No damages or injuries were reported.

See the report at this link:

http://earthquake.usgs.gov/earthquakes/eventpage/usc000mflh#summary

A magnitude 3.0 earthquake shook Azle north of Fort Worth on Jan. 29.

With more than two dozen quakes in North Texas since November, area residents are pressing the Texas Railroad Commission to find out if the temblors are related to hydraulic fracturing, or “fracking.” In that process for extracting gas, hundreds of thousands barrels of water and sand are forced into underground pockets to fracture the rock and release the fossil fuels.

The wastewater created by fracking must be disposed of, usually by drilling disposal wells.

According to the trade publication Platts Gas Daily, the quakes occurred “in the midst of the Barnett Shale play near six active and two inactive wastewater injection wells.”

The Barnett Shale, a geological formation considered the nation’s largest onshore natural gas field, stretches across the “core counties” of Denton, Johnson, Tarrant and Wise. Secondary counties for Barnett Shale drilling include those in the Cross Timbers region – Bosque, Comanche, Eastland, Erath, Hamilton, Hood, Palo Pinto and Somervell.

A 2012 UT Austin study found correlations between disposal injection wells and small earthquakes.

A 2012 UT Austin study found correlations between disposal injection wells and small earthquakes.

The recent “swarm” of North Texas quakes, as experts call them, has been concentrated around the towns of Azle and Springtown, although a 3.7 magnitude quake was recorded in Mineral Wells in December. Last month the railroad commission, which regulates the Texas oil and gas industry, held a town hall meeting at Azle High School to hear residents’ concerns.

Afterward the commission announced it was hiring a seismologist to investigate any connection between the quakes and natural gas and oil drilling in the area.

Rep. Jim Keffer, R-Granbury, also was appointed chairman of a new Texas House Subcommittee on Seismic Activity on Jan. 16.

Earthquakes once were rare in North Texas.

“Most of North America east of the Rocky Mountains has infrequent earthquakes,” the USGS said in its report attached to the Benbrook quake.

“There is evidence that some central and eastern North America earthquakes have been triggered or caused by human activities that have altered the stress conditions in earth’s crust sufficiently to induce faulting,” the report also said.

Those activities include impounding water behind dams, injecting fluid into the earth’s crust, extracting oil or gas or removing rock in quarry or mining operations, the USGS said.

However, the agency noted that making a “strong scientific case” for a link between human activities and particular earthquakes requires specific special studies.

Residents near fracking locations have written letters to the railroad commission to request stricter standards of injection wells.

Energy industry officials repeatedly have claimed that fracking is safe. But researchers have identified cases where injection wells appeared to contribute to earthquakes when fluids get into a fault in the earth’s crust.

A 2012 study conducted by The University of Texas with Austin and supported in part by the U.S. Geological Survey found that most earthquakes in the Barnett Shale region of North Texas “occur within a few miles of one or more injection wells used to dispose of wastes associated with petroleum production such as hydraulic fracturing fluids.”

“You can’t prove that any one earthquake was caused by an injection well,” Cliff Frohlich, senior research scientist at the university’s Institute for Geophysics, said in the report. “But it’s obvious that wells are enhancing the probability that earthquakes will occur.”

The study did not evaluate possible links between earthquakes and the actual fracking process.

Most earthquakes identified in the study ranged in magnitude from 1.5 to 2.5, which generally are not strong enough to cause damage or pose a public danger, the report said.

 

 

 

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