Researchers Ponder Injection Triggered Earthquakes in Texas

Researchers collecting seismic data hope it allows them to determine what role wastewater injection wells have played in a string of small earthquakes northwest of Fort Worth.

The area in northeast Parker County, about 15 miles northwest of Fort Worth, has experienced more than 30 small earthquakes since November. Last month more than 30 area residents traveled to Austin to ask the Texas Railroad Commission to consider shutting down injection wells there, but the commission said it didn’t have enough information.

“We want to get to a point where we can say, ‘This particular well affected this seemingly dead fault,”‘ Heather DeShon, an associate professor of geophysics at Southern Methodist University told the Fort Worth Star-Telegram. “But first we have to gather the data.”

DeShon said the school’s network of seismic activity sensors in an area about 15 miles northwest of Fort Worth have detected numerous small earthquakes recently. Still, it could take a year or more before researchers could tie the earthquakes around the town of Azle to injection wells in the area.

Oil wells often produce tons of salt water, which is pumped back into the ground through the so-called injection wells, to extract more oil. According to the Texas Railroad Commission, there are about 35,000 active injection wells in the state. About 7,000 of those are used for disposal. Experts have said it’s rare for the wells to produce seismic events, but it does happen.

There are five disposal wells around Azle.

Small earthquakes that occurred at the Dallas-Fort Worth airport from October 2008 to May 2009 stopped after one company shut down one of the two injection wells it operated on the airport property.

University of Texas researchers studied seismic data gathered in the Barnett Shale between 2009 and 2011. Cliff Frohlich, senior research scientist at the university’s Institute for Geophysics, concluded that “injection-triggered earthquakes are more common than is generally recognized.”

About 850 area residents attended a community meeting on the earthquakes in early January. The Railroad Commission later voted to hire its own seismologist.

About 30 residents of northeast Parker County went to Austin later in January to ask the commission to consider shutting down the injection wells in their area. Commission members said they didn’t have enough information to do that. Agency officials said they had inspected 11 injection wells in the area. One was being repaired, but the others were in compliance with their permits.