WASHINGTON -- A cluster of earthquakes in Texas may be tied to oil companies injecting carbon dioxide into deep rock formations in the area, according to a paper released Monday.
The study, published in Proceedings of the National Academy of Sciences, is one of the first to look closely at the potentially earth-shaking repercussions of injecting carbon dioxide underground, both to store the greenhouse gas and help enhance oil recovery. And it is the first to document a correlation between earthquakes greater than magnitude 3 with the gas injection process that many believe is valuable for combating climate change.
University of Texas seismologist Cliff Frohlich, who led the research into the Texas quakes, cautions that the science is new and there is plenty more investigating to do. But similar findings could throw cold water on policymakers' enthusiasm for capturing carbon dioxide and indefinitely storing the heat-trapping greenhouse gas underground.
Mr. Frohlich and fellow professor Wei Gan said gas injection at the Cogdell oil field north of Snyder, Texas may have sparked as many as 18 earthquakes with magnitudes of 3 and greater between 2006 and 2011 -- including one that registered 4.4 on the magnitude scale.
"Gas injection may have contributed to triggering a sequence of earthquakes occurring since 2006," they said. "This is an unusual and noteworthy instance where gas injection may have contributed to triggering earthquakes having magnitudes of 3 or larger."
The small temblors took place at a time when energy companies were increasingly using carbon dioxide to help extract oil from the Cogdell field, an activity that began in the area in 2001, but which Mr. Frohlich and Mr. Gan said "has been ongoing with nearly constant injection volumes since 2004."
Oil companies can boost their recovery of crude by sending gas underground to displace crude. Although other gases can be used, carbon dioxide is favored because of the way it interacts with oil underground.
Energy Secretary Ernest Moniz has touted the potential of carbon dioxide to boost U.S. oil recovery, while at the same time indefinitely storing the greenhouse gas. While the U.S. is now producing about 300,000 barrels per day using carbon dioxide at older fields, Mr. Moniz has said that could grow to about 3 million barrels a day, as long as there's enough CO2 captured from power plants and industrial facilities to support it.
The Energy Department is working to accelerate some enhanced oil recovery technology and operations. For instance, it has provided about $431 million toward a project at Valero's refinery in Port Arthur, Texas, where carbon dioxide is now being extracted from two steam methane reformers, then dried, compressed and shipped to the West Hastings oil field 20 miles south of Houston.
Separate research is underway to document whether today's drilling boom -- including the use of horizontal drilling and hydraulic fracturing -- may be causing quakes near oil wells. England imposed an 18-month moratorium on hydraulic fracturing after concerns about quakes from the process that involves pumping water, sand and chemicals underground to free trapped oil and gas.
But recent studies suggest hydraulic fracturing itself is not to blame for significant quakes. Instead, quakes near oil fields are more likely to be tied to disposing of drilling wastewater in underground injection wells.