By Erin Ailworth
Texas regulators have ordered a subsidiary of Exxon Mobil Corp.
and another company to prove that their wells near Fort Worth
aren't causing earthquakes.
A study published this week by seismic researchers at Southern
Methodist University in Dallas connected two wastewater disposal
wells operated by XTO Energy Inc., which is owned by Exxon, and
EnerVest Operating LLC, with a series of earthquakes in Azle,
Texas. On Friday the Texas Railroad Commission, which regulates the
state's oil and gas industry, told officials at both companies that
they need to appear at hearings scheduled for June to justify why
their wells shouldn't be shut down.
Azle, 17 miles northwest of Fort Worth, experienced a string of
earthquakes between November 2013 and January 2014 that were most
likely caused by high volumes of drilling wastewater injected deep
into the ground as natural gas was pumped out, the study said.
The Railroad Commission of Texas said it is reviewing SMU's
research.
The process of hydraulic fracturing, in which water, chemicals
and sand are pumped into the ground under high pressure, results in
large volumes of wastewater. Leftover wastewater is often pumped
back underground into so-called disposal wells, which have been
linked to earthquakes by several studies.
XTO said it looked forward to discussing the issue with
regulators and university researchers. "We follow a protocol, a
scientific-based protocol, when we site our disposal wells," said
Suann Lundsberg, a spokeswoman for the company.
EnerVest cast doubt on the SMU study. "We have serious questions
about some of the assumptions in the SMU paper, and we look forward
to sharing these with the Commission," said Ron Whitmire, a company
spokesman.
Critics of fracking have questioned whether the industry's
practices are to blame for an increase in earthquake activity in
states such as Texas.
Meantime, new scientific findings released Tuesday again linked
earthquakes to the practice of injecting wastewater from oil and
gas operations deep underground, adding to a growing consensus
among researchers that energy development is probably causing
seismic activity in Oklahoma, Texas and other parts of the U.S.
In October, the Texas Railroad Commission adopted regulations on
wells used to dispose of drilling fluids. Under the rules, enacted
to protect against possible earthquakes caused by the wells, a new
disposal well can't be sited without an evaluation of data from the
U.S. Geological Survey about the earthquake history within a
100-square-miles around the proposed site.
The new rules also give regulators the power to modify, suspend,
or end a disposal well permit if scientific data show that it is
contributing to earthquake activity, or is likely to do so.
The commission said those amended rules are one reason it is
asking questions about the XTO and EnerVest wells.
"It is incumbent upon us to apply these rules where and when
appropriate for the protection of public safety and our natural
environment," said Christi Craddick, chair of the commission. "In
light of SMU's study linking disposal well activity to earthquakes
in 2013, it is important to assess this new information in relation
to the continued operational safety of the wells."
The commission previously investigated whether these disposal
wells near Azle were contributing to earthquakes, but didn't
uncover evidence of a definitive connection.
Write to Erin Ailworth at Erin.Ailworth@wsj.com
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