Chesapeake still doubts that quakes, disposal site are linked

By Bill Hanna and Alex Branch

Star-Telegram Staff Writers

Editor's note: This report was originally published Aug. 15, 2009.

Calling their company’s decision to shut down two disposal wells "strictly precautionary," Chesapeake Energy officials said Friday that they remain skeptical about any link between small earthquakes near D/FW Airport and a saltwater disposal site on the airport’s southern end.

Julie Wilson, a spokeswoman for Chesapeake, said it is too early to say how long the disposal wells -- one at D/FW and another in Cleburne in Johnson County -- will remain closed while their own scientists study the issue. Both were shut down Tuesday.

But Wilson said Chesapeake officials said they do not believe that there is a connection between the disposal wells and a rash of seismic activity around D/FW. Quakes were recorded near the airport late last year and in the spring.

"We truly question any correlation," Wilson said.

Researchers at the University of Texas and SMU, who have been studying the quakes in both locations, said that initial evidence appears to show a connection but that their research is far from over.

"Nothing has changed since May," said Cliff Frohlich, a University of Texas seismologist who co-authored a book on Texas earthquakes. "All I can tell you is there were earthquakes within a few weeks after they completed a disposal well near that fault. That is the focus of our research but it’s too early to draw any conclusions."

Frohlich said researchers are still at least a month or two away from publishing results in academic journals that are subject to peer review.

SMU officials referred Friday to a statement by seismology professor Brian Stump a day earlier that said that "initial studies show a possible correlation" but that "it is premature to state unequivocally that saltwater disposal at this well is responsible for the earthquakes."

Disposal wells "seem to be a more probable cause of some earthquakes rather than from hydraulic fracturing, a process used in preparing the wells for gas production," Stump said. "But more study is needed."

Disposal wells take salt water that has been used to crack rock to reach natural gas and reinject it into the ground.

The Texas Railroad Commission, which regulates oil and gas activity in Texas, said it first learned Thursday that the disposal wells had been "shut in" and was inspecting the sites, spokeswoman Ramona Nye said.

"As the investigation progresses, if information from the university earthquake research indicates possible concerns regarding the commission’s current permitting processes and rules for disposal wells, the commission will take that into consideration as it reviews the issue," Nye said.

In the Barnett Shale, 12,050 wells have been drilled, and 101 disposal wells have been permitted, Nye said.

For residents of Cleburne, which has had minor quakes in recent months, the latest revelations brought few answers. Though Chesapeake shut down a disposal well in Johnson County, the preliminary data dealt only with seismic activity near D/FW.

"The way I understand it, the data from Cleburne isn’t in yet," Cleburne Mayor Ted Reynolds said. "It is a little confusing, to be honest with you. We haven’t been privy to any of the scientific information."

City officials appreciate Chesapeake’s closing the Cleburne disposal well as a precaution, he said. Chesapeake has been a good corporate citizen and seems as eager to identify the cause of the earthquakes as the city does, he said.

"Chesapeake must have thought there may be some kind of a link," Reynolds said.

To call most residents "concerned" about the earthquakes is going too far, he said. Because the earthquakes have caused no damage, residents are more curious as to the cause.

"As a city government, of course, we want to know what is causing this," Reynolds said.

David Magana, a spokesman for D/FW, said airport officials are in the final stages of approving an agreement with SMU scientists to set up seismology equipment on airport property.

They started working on the agreement in May and are just finalizing liability issues, he said.

"We fully support the idea of bringing in seismology equipment," Magana said. "We are very committed to being a good neighbor and have demonstrated that over and over with our commitment to environmental issues."

Magana said he did not know whether there were any discussions about the fault line before the disposal well was created. He pointed out that drilling at the airport is subject not only to all state drilling regulations but also the added scrutiny of the Federal Aviation Administration.

"I know that a great deal of research was done," he said.

TCU geologist Ken Morgan, director and associate dean of the TCU Energy Institute, said: "As I understand it, the fault found near the southern end of D/FW was discovered by relatively recent seismic surveys carried out before drilling. Its depth and orientation are indicative of other rather deep faults found below the Barnett Shale throughout the counties in North Texas."

Morgan said it is prudent to stop the injections while the issue is studied further. If the disposal and the quakes are related, Morgan said, "sometimes just reducing disposal volumes, rates or pressures can alleviate even minor quakes."

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