Just when you thought no other ugly issue could rear its head (e.g., lizards and chickens), we have, from the land of Senator Wendy Davis, claims that hydraulic fracturing is causing earthquakes. There is no disputing that there has been an increase in tremors registering as high as 3.6 in magnitude over the past three months near the town of Azle, Texas, (pop. 10,000), located 16 miles northwest of downtown Fort Worth. Tremors in the 2.0-3.9 magnitude are considered “minor” with the effect of “Experienced, but no damage caused” per the National Earthquake Information Center. Having said that, I must acknowledge that earthquakes are a frightening experience at any level. One never knows who made the linkage, but a spirited group of area residents met on January 2nd at the Azle Community Center to voice their concerns that the tremors are being caused by gas well completions in the Barnett Shale in the area. “There is no question what is causing it,” said John McGee, who lives in the area and says fracking is the only reasonable explanation. “We never had them before. Never.” (as reported by Todd Unger/WFAA)
Fortunately, Texas Railroad Commissioner David Porter and some of his staff had the guts to attend the community meeting in Azle. He announced that the Texas Railroad Commission (RRC) would hire a seismologist to assess the surge in tremors. Recently, the RRC has published a report, dated January 24, 2014, by Milton Rister, Executive Director of the RRC, updating the public on seismic activity in Texas and the RRC’s plans to assess the activity and potential causes. The report focuses on the saltwater disposal (SWD) wells in the area as opposed to gas well completions. One interesting note is that the United States Geological Survey (USGS) National Earthquake Information Center’s sensing equipment is so sparsely distributed that its accuracy in pinpointing the seismic activity was “relatively imprecise” (in the words of the USGS) and indicated rather wide dispersion. SMU was engaged by the USGS and located its geophones more closely to the activity and defined a much tighter radius of activity northeast of Reno, Texas. The refined area of activity is offset within 1-2 miles by two non-commercial saltwater disposal (SWD) wells. Of further interest is the fact that the SWD wells are permitted to 10,000 and 25,000 barrels per day, respectively. No mention is made in either the USGS/SMU study or the Railroad Commission report about a linkage of the tremors to hydraulic fracturing or the production of oil and gas. It would be interesting to know the cumulative water disposed in each well.
State Representative Jim Keffer, Chairman of the Texas House Committee on Energy, has formed a Subcommittee on Seismic Activity chaired by Representative Myra Crownover of Denton County, which is less than 20 miles from Reno and Azle. My hope and expectation is that they will rely heavily upon the expertise and efforts of the Railroad Commission to examine the science behind the tremors. The Railroad Commission hosted a meeting in Austin open to the public and attended by representatives from Azle and Reno on January 21, 2014. The RRC is following up with the citizens that voiced concerns and has an open door policy to address future concerns.
Now, a few facts extracted from the aforementioned RRC report. One, the saltwater disposal appears to be limited to the Ellenberger formation, a porous and permeable dolomite at the bottom of the geologic column above the basement rock. The injection interval ranges from 5300’ to 8700’ subsurface. The Barnett Shale ranges in depth from 4750’ to 6900’ above the Ellenberger. The RRC identified 13 SWD wells in the area, of which 12 are active. The 13th was properly plugged last year. All 12 active SWD wells had no pressure on the tubing-casing annulus or surface casing, and the RRC inspectors did not find that injection fluids were escaping the disposal interval. The RRC’s jurisdiction is generally over threats of water pollution, but does not have jurisdictional authority to shut down a well based only on the presence of nearby seismic activity. However, the RRC can shut in a well if there is an indication of injection fluids escaping the disposal interval.
From the RRC report: “To date, research on the possible role of oil and gas operations on induced seismicity is inconclusive and at times contradictory. By bringing in an in-house seismologist, the Commission hopes to gain a clearer understanding of the issue. RRC rules and regulations must be based in science and fact. To date, no RRC violations have been identified.”
The following comments were extracted from various experts, as cited by the RRC in their January 24, 2014, report.
From Cliff Frohlich, Senior Research Scientist at the Institute for Geophysics at the University of Texas at Austin:
“You can’t prove that any one earthquake was caused by an injection well.”
“It might be that an injection can only trigger an earthquake if injected fluids reach and relieve friction on a nearby fault that is already ready to slip. That just isn’t the situation in many places.”
From the December 2013 SMU research report commissioned by the USGS:
“…the possibility exists that earthquakes may be related to fluid injection.”
“It’s definitely a maybe. It’s one of those things that you can’t really prove.”
“…a wastewater injection well was a ‘plausible cause’ for a series of earthquakes in North Texas.”
From the National Academy of Sciences’ “Induced Seismicity Potential in Energy Technologies,” June 2012:
“The process of hydraulic fracturing a well as presently implemented for shale gas recovery does not pose a high risk for inducing felt seismic events.”
“Injection of disposal waste water derived from energy technologies into the subsurface does pose some risk for induced seismicity, but very few events have been documented over the past several decades relative to the large number of disposal wells in operation.”
In their study, “Ongoing Seismicity at Dallas-Fort Worth Area,” Dr. Leo Eisner and Eva Janska, geophysical and microseismic experts, found seismic activity continued long after a well suspected of inducing seismic activity in the DFW area was shut in. Event detection based on cross-correlation shows that the seismic activity has been continuous for more than two years after the salt-water disposal injection ceased (August 2009). In their 2012 report, “Ongoing Seismicity at Dallas-Fort Worth Area,” the same authors conclude: “It is difficult to understand how increased pressure due to injection could trigger significant seismicity more than two years after the injection considering the rapid decline of injection pressure. The seismic activity in the DFW area in 2008-2010 might be triggered [but certainly not induced] by the SWD injection. However, it is more plausible that the seismic activity occurs naturally at this region and the observed seismicity is part of natural migration of microseismic activity from south to north.”
The Railroad Commission’s next steps include “providing maps and data on its website, continuing to work with SMU and the USGS, hiring a seismologist who will examine all causes of seismic activity, requesting information from industry operators and experts, and continuing outreach to academic experts. The RRC will work with the House Subcommittee on Seismic Activity and take action as warranted based on science and fact.”
We should all be concerned that the seismic events around Azle will be used as a justification for plaintiff’s attorneys and environmental activists to attack hydraulic fracturing and saltwater disposal on yet another front. Yet, we should be thankful that the Railroad Commission is vigilant in its examination of the facts and reliance on unbiased experts who seek the truth. Be sure to thank your Texas Railroad Commissioners and employees for their efforts in this sensitive matter.