By CHRISTIN COYNE
Scientists have known for some 50 years that injection can lead to seismic activity, according to one researcher studying the Azle earthquakes.
However, it’s not always an easy thing to determine whether a particular injection well is or isn’t causing earthquakes and USGS researcher William Ellsworth, a geophysicist working with a research team from SMU and other colleagues to study the dozens of recent small earthquakes near Azle, isn’t making any promises.
“The scientific evidence has really been very conclusive since the 1960s about how injection can induce earthquakes,” Ellsworth said. “It doesn’t prove that any particular well is responsible but the mechanism is well understood. And often what we lack is enough information to really tie pieces together to associate activity with a particular well or to rule out an association.”
Researchers aren’t sure when they may have more information to present to the community regarding the Azle earthquakes.
“It all depends on what data may tell us and interpretations of these kind of results often contain some ambiguity so we can’t promise something that we can’t deliver,” Ellsworth said.
Injection wells are used to inject into the ground, through layers of rock and shale, waste fluids used in oil and gas drilling operations. There are reportedly several injection wells in the area near Reno that officials have cited as the epicenter of the recent Azle-area quakes.
Ellsworth couldn’t say whether the seismic activity in the area might have been triggered by human activity.
“Very generally, we do know that there are tectonic earthquakes, natural earthquakes, that occur in Texas so I don’t think that anyone has jumped to the conclusion that these are induced at this point,” Ellsworth said.
However, he did note that after scientific studies of earthquakes in the Barnett Shale, Prof. Cliff Frohlich, the senior research scientist at the Institute for Geophysics at the University of Texas in Austin, found many of the recent earthquakes are associated with injection.
Frohlich found it plausible that earthquakes in the Cleburne area were triggered by injection in the area.
Other studies across the nation are indicating a possible connection between injection and earthquakes over 3.0 and into damaging magnitudes. Though researchers haven’t reached a consensus on what caused the magnitude 5.6 earthquake in central Oklahoma in November 2011, some scientists believe wastewater injection into a depleted oil field likely played a role.
A Youngstown, Ohio earthquake of magnitude 4.0 in 2011 was linked to injection and regulators shut down a well believed to be responsible.
A University of Memphis researcher found a correlation in 2011 between a series of earthquakes in Arkansas and injection wells.
Researchers have studied possible injection-triggered earthquakes in other areas of Texas, as well.
A study published by Frohlich in 2013 found that “timing of gas injection [in the Cogdell oil field near Snyder] suggests it may have contributed to triggering the recent seismic activity.”
More than 18 earthquakes of a magnitude 3 or greater were reported between 2006 and 2011 in the area of Snyder. Frohlich’s study noted that a prior study of earthquakes between 1975 and 1982 in the area found that water injection to enhance oil production induced a series of earthquakes, as well.
Researchers also studied a magnitude 4.8 earthquake near Fashing and a 4.9 quake near Timpson.
“Quantifying their contribution presents difficult challenges that will require new research into the physics of induced earthquakes and the potential for inducing large-magnitude events,” Ellsworth wrote in a July 2013 review paper in Science Magazine on the topic. “The petroleum industry needs clear requirements for operation, regulators must have a solid scientific basis for those requirements, and the public needs assurance that the regulations are sufficient and being followed.
“The current regulatory frameworks for wastewater disposal wells were designed to protect potable water sources from being contamination and do not address seismic safety,” Ellsworth added. “One consequence is that both the quantity and the timeliness of information on injection volumes and pressures reported to regulatory agencies are far from ideal for managing earthquake risk from injection activities.”
Also, seismic monitoring capabilities in some areas where injection has increased are not capable of detecting smaller seismic activity that may presage larger earthquakes, according to Ellsworth.
One way that some have proposed to attempt to prevent larger earthquakes is a “traffic light” system of reducing injection rate or pressure if earthquakes of a certain magnitude occur or stopping injection if seismic activity increases.
But researchers feel they need more kinds of information that might not be available as they conduct more research on the complex topic and seek to develop a predictive understanding of the hazard posed by induced earthquakes.
“The Railroad Commission does collect the information that is required by federal law and that is valuable,” Ellsworth said. “From a research standpoint, we think that the frequency of reporting injection information could be improved, but that’s a regulatory issue.”
Despite various studies on the topic in recent years, the Texas Railroad Commission doesn’t appear to recognize any scientific consensus on the issue.
“RRC staff welcomes more data and science about current theories that hypothesize a causation link between minor seismic events and injection wells,” statement on the RRC website reads. “RRC staff is closely following various studies that are being conducted to determine possible man-made causes of recent seismic events. Commission staff has participated in industry workshops concerning this phenomenon and cooperates with the National Academy of Sciences and the U.S. Environmental Protection Agency whenever appropriate.”
“Seismic waves are continuously traversing the earth’s crust due to both natural causes and human activity. Texas has a long history of safe injection, and staff has not identified a significant correlation between faulting and injection practices.”
Information on how much fluid has been injected since the beginning of October by at least one injection well operator in the area of the earthquakes isn’t yet available because the operator’s annual reporting cycle ended in September and that information isn’t yet due to the Texas Railroad Commission, the commission confirmed for the Democrat this past week.
Asked whether the RRC plans to consider requesting any area well operators to decrease or stop injections until the issue of possible cause can be studied, a railroad commission spokeswoman replied: “The commission bases its regulatory actions and rules on sound science and proven facts and is in the process of hiring a seismologist to study the issue.”
Earthworks, a group calling for more oil and gas industry regulation, has organized a bus trip to take Azle-area residents calling for more immediate action on the issue from the RRC to Austin Tuesday morning to speak at the regular railroad commissioners’ meeting and with legislators.