Exxon Says It Didn't Cause Texas Quakes

AUSTIN—Exxon Mobil Corp. told Texas regulators Wednesday that the company's operations aren't behind a string of earthquakes in the Dallas-Fort Worth area.

In the first hearing of its kind for the Railroad Commission of Texas, officials with Exxon subsidiary XTO Energy Inc. presented engineering and geological data they said show quakes that hit one suburb in 2013 originated far deeper than a nearby well the company used to inject wastewater from oil-and-gas operations back underground.

"Those are deep-seated basement fault movements," said Tim George, a lawyer for the company. "These are naturally occurring movements, not man made."

A sharp increase in the number of earthquakes in the northern part of Texas prompted the commission, which oversees oil-and-gas industry activity, to launch a series of hearings on the topic. EnerVest Operating Co., which operates a wastewater well in a Fort Worth suburb is scheduled to appear before state examiners next week. Four other energy companies, including EOG Inc., have been asked to perform tests on several wastewater wells near Venus, 30 miles south of Dallas, where a magnitude 4.0 earthquake struck in May.

EnerVest also disputes its well's role in causing the earthquakes near the Fort Worth suburb of Azle. After reviewing geological data, the company believes some were aftershocks from a deeper, naturally occurring tremor, said Jud Walker, chief operating officer.

"The conclusions they drew were a little strong," Mr. Walker said of the SMU study.

Earlier this year researchers at Southern Methodist University in Dallas published a study linking a cluster of earthquakes in the Azle area between November 2013 and January 2014 to wastewater wells operated by XTO and EnerVest. SMU researchers stand behind that report, and said Wednesday that fault networks act as paths for pressure changes to travel to critically stressed areas and trigger earthquakes.

The wells aren't directly connected to drilling or hydraulically fracturing oil and gas wells. Wastewater wells are used to inject dirty water back underground that is left over from fracking operations, as well as brine water that gets pumped out of oil and gas wells. Those injections, SMU researchers say, likely contributed to subsurface pressure changes that triggered earthquakes near Fort Worth.

Studies done as far back as the 1960s have linked injection wells to earthquakes deep in the ground, said Bill Ellsworth, a geophysicist with the U.S. Geological Survey who worked on the SMU research.

"That's where induced earthquakes usually occur," he said. "This is science that has been understood for 50 years."

The U.S. Geological Survey says injection wells can cause earthquakes, though not all do; such induced quakes can happen miles away from the injection site.

Earthquakes big enough to feel were virtually unknown to the Dallas-Fort Worth area until this decade when drilling and fracking activity soared in the area, which is home to the gas-rich Barnett Shale. The quakes have become common enough that some schools in the region have begun to drill children on how to shelter under their desks.

There has been a dramatic rise in tremors across the central U.S. over the last six years, primarily caused by wastewater disposal wells, according U.S. Geological Survey data. Between 1973 and 2008, the region averaged 24 quakes of magnitude 3 and larger each year. But between 2009-14 that rate has steadily increased to average 193 a year, peaking in 2014 with 688 earthquakes.

Texas regulators revised permitting rules last November so they could modify, suspend or even end a wastewater disposal well's approval if scientific data showed it could be contributing to earthquakes.

The Railroad Commission's scrutiny will continue said Commissioner Ryan Sitton. The increased frequency of earthquakes in Texas is a big concern, he said, noting they are happening both close to and far from oil-and-gas operations.

"We need to research it," Mr. Sitton said, acknowledging that public fear of the earthquakes has led some communities to try to ban the industry from their towns. "We have an opportunity to keep this from becoming a political issue."

Write to Erin Ailworth at [e-mail]

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