November 5, 2013
Texas Tremors Likely Triggered By Gas Injection Processes: Study
Michael Harper for redOrbit.com - Your Universe Online
A newly published study has confirmed a series of small earthquakes that shook the west Texas town of Snyder can be blamed on a production process in the oil fields.
In 2004 workers at the Cogdell Oil Field began injecting their wells with carbon dioxide as a way to increase production, a method that researchers now say was responsible for a spate of earthquakes that shook the area between 2006 and 2011.
This is not the first time the oil field has been blamed for earthquakes in the small Texas town located about 80 miles northwest of Abilene. Waste water injection practices has been blamed for tremors that also affected the region between 1975 and 1982. Because such practices could not be linked to the new rash of activity, scientists were curious to know what could be behind the recent Texas earthquakes.
This new study, conducted by researchers at China University and the University of Texas in Austin, is the first to link carbon dioxide (CO2) injections with seismic activity. Though the link has been confirmed, however, the practice doesn’t always result in earthquakes. The team has published their paper in the journal Proceedings of the National Academy of Sciences (PNAS).
“The timing of gas injection suggests it may have contributed to triggering the recent seismic activity,” explained the study authors. "If so, this represents an instance where gas injection has triggered earthquakes having magnitudes 3 and larger."
The new study investigated the operations at the Cogdell oil field and two others in the area with funding from the Department of Energy. As CO2 had been injected in these fields for many years at such great quantities, the Department of Energy wanted to investigate the effects of this practice as well as the future of a proposed technique called carbon capture and storage (CCS) on the environment.
Cliff Frohlich, study co-author and associate director of the Institute for Geophysics at the University of Texas at Austin said the possibility of these practices affecting the region around the fields is strong and was demonstrated during the 2006 through 2011 quakes.
"I'm not an expert on climate engineering, but a number of solutions have been proposed," said Frohlich in an interview with National Geographic's Joe Eaton. "Whether they are good ideas or not, the jury is still out. Anytime you mess with the environment, there are unintended consequences.”
Using data captured by a network of high-resolution seismometers located in the area near the Cogdell oil field, Frohlich and team identified a total of 93 earthquakes of various magnitudes between March 2009 and December 2010. Three of these quakes topped the scale at a magnitude of 3 or greater, and one in September 2011 registered at a magnitude of 4.4. When they combined this data with the amount of gas injected and retrieved from the field at the same time, they deduced that the two were linked.
Curiously, they also found that the practice of injecting CO2 into the ground doesn’t always lead to earthquakes.
“What’s interesting is we have an example in Cogdell field, but there are other fields nearby that have experienced similar CO2 flooding without triggering earthquakes. So the question is: Why does it happen in one area and not others?” said Frolich in a statement.
Though previous research has suggested there is a direct correlation between high injection rates of gasses and earthquakes, Frolich says areas that lie on certain geological faults — like Snyder, Texas — are more likely to experience an earthquake in any event, and the gas injection only spurs this.
The next step, says Frolich, is to create a geological model of the Cogdell oil field and those around it to understand how future CO2 injections and retrieval methods will affect the surround communities.