The Texas Railroad Commission on Friday said pressure testing of five disposal wells in Johnson County did not provide any conclusive evidence that they played a role in triggering a 4.0 magnitude earthquake located near Venus last month.
Expert analysis by the Railroad Commission’s staff seismologist, geologists and petroleum engineers tested five wells within 100 square miles of the estimated epicenter of the seismic event as set out by the commission’s new rules on seismicity that were adopted last year.
The tests, which were conducted to help determine the effect of oil and gas operations on pressures within subsurface formations, did not indicate any bounding faults in the immediate vicinity of the wells tested, the commission reported.
“We appreciate the cooperation of the operators to voluntarily shut down and collect data that will help us better understand what, if any, relationship there is between these wells and seismicity,” said Craig Pearson, the commission’s seismologist, said in a prepared statement.
“While we can’t say at this time there is a connection, this is the beginning of the process, not the end in analyzing and understanding whether there is any correlation and what, if any, action by the Commission may be necessary in the future to protect public safety and our natural resources,” he said.
The earthquake occurred around 6 p.m. on May 7 and was centered about 6 miles south of Mansfield and about 3 miles northwest of Venus, according to the U.S. Geological Survey.
The temblor was the most powerful of more than 50 quakes that have rumbled through North Texas over the past 18 months, officials said.
Immediately after the earthquake, the Railroad Commission, which regulates the oil and gas industry in the state, asked four operators to shut down the five wells. Bosque Disposal System, MetroSaltwater Disposal and Pinnergy all had one well within the area. EOG Resources had two.
Last year, after a rash of earthquakes in North Texas, the Railroad Commission approved rules Tuesday requiring drillers to provide additional information before sinking injection wells in areas where there has been seismic activity.
Drillers seeking a permit also are required to provide information on the history of seismic events as recorded by the U.S. Geological Survey. The rules also allow the Railroad Commission to suspend or terminate a permit if seismic activity occurs near an injection well.
Using the same rules, the state is considering shutting down two wastewater injection wells linked by a recent scientific report to a rash of earthquakes northwest of Fort Worth.
This week, XTO Energy at a “show cause” hearing refuted the claims made in a study by Southern Methodist University that its disposal well was linked to the series of earthquakes in the Reno and Azle area from November 2013 to January 2014.
XTO officials testified that the earthquakes were naturally occurring and far deeper than where the wastewater was injected. They also said that the Barnett Shale, which covers 5,000-square-miles of North Texas, has had several episodes of movement and reactivation of faults.
EnerVest Operating will testify at a similar hearing next week. Officials from that company also have rejected the findings of the SMU study, saying the university’s findings did not match their own review of the data.
SMU is standing by its report, however. While they won’t comment on the Railroad Commission hearings, but said in a statement that they “remain confident in the conclusions presented in our peer-reviewed publication, which was based on multiple lines of evidence.”
Max B. Baker, 817-390-7714