Earthquakes in Texas get the attention of Louisiana agency
by Jen DeGregorio, The Times-Picayune
Sunday July 05, 2009, 6:36 AM

A series of minor earthquakes recorded as recently as last week in Texas have raised the specter of tremors in northwest Louisiana, where a natural gas discovery has launched a gold-rush style drilling boom.

A similar rush hit north Texas several years ago, after geologists found vast stores of natural gas in the Barnett Shale, a layer of underground rock spanning 5,000 square miles. Thousands of wells have been drilled, and some scientists have blamed the recent earthquakes on the intense process used to extract gas from the shale, called fracturing.

Developers are using the same process in Louisiana on the Haynesville Shale, which spreads beneath a six-parish region near Shreveport. Prospectors began flocking to the area early last year, after an energy firm announced that the Haynesville Shale could be the largest natural gas reserve in the country.

Louisiana's Department of Natural Resources has its ear to the ground for more rumblings from Texas. But until scientists can draw a firm link between drilling and the earthquakes, state regulators have no plans to discourage gas production in the Haynesville Shale, where hundreds of wells have been drilled and hundreds more are planned.

"We'd need to hear someone say, 'Yes, there is a tie,' before we move forward," said Patrick Courreges, a spokesman for the department.

It is nearly impossible to pinpoint the cause of an earthquake, said Cliff Frohlich, associate director of the Institute for Geophysics at the University of Texas at Austin. But fracturing seems the likely culprit, given the low instance of fault activity in north Texas before the Barnett Shale drilling boom.

"It sure looks like it's related," Frohlich said.

Fracturing involves drilling deep into the shale, then blasting streams of water into the hole to break the rock and release the gas.


That kind of pressure can shake otherwise stable fault lines, said Barry Cole, an adjunct geology professor with Tulane University. Water further complicates matters because it acts like a lubricant, causing rocks lodged together at a fault to slip out of place.

"Any injection near the fault plane could trigger an earthquake," Cole said.

The wave of tremors in north Texas began in the Dallas-Fort Worth area in October. The quakes have been small, no higher than 3.3 on the seismic scale. Some have been imperceptible to people on the ground, while others caused slight vibrations.

"As far as we know, there's been no damage," Frohlich said. "These are very minor."

Still, a team from Southern Methodist University is trying to figure out whether the drilling has set off the quakes. The scientists are planting seismic meters, which can identify the depth and location of an earthquake, at various spots in north Texas. Some will be placed in Cleburne, a small city about 60 miles southwest of Dallas, where the mayor and City Council have called for a study.

News about the earthquakes has just reached officials in Caddo Parish, where there has been a flurry of Haynesville-related drilling in the last year. Assistant Administrator Randy Lucky, who did not know about the quakes until a reporter called for an interview this week, said he would raise the issue with parish officials.

"We will have a little discussion," Lucky said.

Like Texas, Louisiana is not known as earthquake country. The state experienced 43 "felt events" between 1843 and 1994, ranging between 2 and 4.4 on the seismic scale, according to a 2001 publication from the Louisiana Geological Survey.

"If it is related to the fracturing .Â¥.Â¥. the chances that that might happen in the Haynesville have to be considered, because it's a similar setting," said Charles "Chip" Groat, a geology professor at the University of Texas at Austin and former director of the Louisiana Geological Survey.

Northwest Louisiana does have several fault lines, and state officials would not be out of line to begin monitoring areas near drilling fields, Groat said. Small quakes can disrupt electrical grids and other underground infrastructure, even if pedestrians may not register a rattle.

"If you have a chance to get ahead of the curve and do some monitoring, you'll have answers when you need them," Groat said.

Jen DeGregorio can be reached at jdegregorio@timespicayune.com or 504.826.3495.

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