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Colorado officials will work with the Interstate Oil and Gas Compact Commission and the Groundwater Protection Council, both based in Oklahoma City, to study links between human-caused earthquakes and deep-well wastewater disposal. Other states participating in the working group are Arkansas, California, Illinois, Indiana, Kansas, Ohio, Oklahoma, Pennsylvania, Texas and West Virginia.
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The oil and gas compact commission is a multi-state governmental agency that seeks to conserve oil and natural-gas resources while protecting health, safety and the environment. The groundwater council is a nonprofit that works with state agencies to protect groundwater. The two organizations have joined forces to explore earthquakes caused by injecting oil and gas wastewater into wells thousands of feet beneath the earth’s surface. They plan to share science, research and practical experience to minimize risk and enhance readiness when quakes occur.
Quakes have increased dramatically in Oklahoma this year, and members of the working group have said they are interested in better understanding the phenomenon. A new U.S. Geological Survey and Oklahoma Geological Survey analysis found that 145 earthquakes of magnitude 3 or greater occurred in Oklahoma from January through May 2. The number of earthquakes during the first four months of 2014 already has broken the record of 109 earthquakes set in 2013.
“A likely contributing factor to the increase in earthquakes is triggering by wastewater injected into deep geologic formations,” said the U.S. Geological Survey and Oklahoma Geological Survey in a statement.
Oil and gas wastewater comes from liquid used in hydraulic fracturing, or fracking, a drilling technique where companies pump millions of gallons of fresh water, sand and chemicals into a drilled hole to extract a mixture of oil and natural gas. Operators have not found a way to economically recycle the leftover water, filled with minerals once it rises to the surface, so they haul it away from the drilling site in trucks and pump it deep underground, where it does not rejoin the water cycle.
The Colorado Oil and Gas Conservation Commission regulates more than two dozen deep-injection wells in the greater Wattenberg area designated specifically for exploration and production waste.
The state oil commission regulates the wells to protect drinking water sources. Injection zones must meet criteria showing that an aquifer is unlikely ever to be used as a source for drinking water and that the well isn’t near sensitive underground faults.
Although most earthquakes in Colorado occur naturally, the state has a unique history related to human-caused earthquakes and deep-well wastewater disposal. No quakes have been directly linked to fracking.
From 1963 to 1967, a series of earthquakes occurred when wastewater was disposed into a 12,000-foot-deep well at the Rocky Mountain Arsenal northeast of Denver. The earthquakes, the earliest known underground wastewater disposal-related tremors, stopped in 1968 after the Army slowly removed wastewater from the well.
Earthquakes at Rocky Mountain Arsenal came before the state developed regulations on injecting wastewater underground. Much of the research done on the subject since then has been conducted in Colorado and has helped the state develop a better understanding of how to reduce human-caused earthquakes.
Wastewater injection from coal-bed methane production in the Raton Basin west of Trinidad may have caused multiple earthquakes during the past few years, including a 5.3-magnitude tremor in August 2011, said Robert Williams, a geophysicist for the U.S. Geological Survey’s Earthquake Hazards Program. The federal agency is researching the subject with help from university researchers.
“There’s lots of wastewater disposal wells, which are what we think is the main culprit, but not every disposal well is producing felt earthquakes,” he said. “We don’t really understand this problem completely, but it’s being actively studied.”
Williams was not aware of any earthquakes able to be felt by people that were caused by oil and gas wastewater injection in Northern Colorado, the most active oil and gas development region in the state.
Nationwide, deep-underground disposal of fracking wastewater poses some risk for increased earthquake activity, but relatively few quakes have been recorded over the past several decades, according to a 2012 study from the National Research Council. Fracking itself poses little risk for causing earthquakes that people can feel.
David Dillon, one of the researchers who conducted the study, said the risk of a deep-injection well causing an earthquake that people can feel is “very small.”
Injection of fluid near cracks in rocks that make up underground fault systems that allow large blocks to move separately can cause earthquakes, he said. Fluids can lower frictional forces that hold these rocks in place, causing rocks along the fault to move.
At the time of the National Research Council’s study, just eight of about 151,000 deep wells used for oil and gas wastewater disposal caused earthquakes, said Dillon, a petroleum engineer who has expertise in deep-injection wells and induced earthquakes.
Most of the earthquakes produced quakes with a magnitude of 4. One of those tremors in Oklahoma registered a magnitude of 5.6 in 2011. The quake caused property damage, but no injuries were reported.
“Only deep faults can store enough energy to produce a large-magnitude earthquake at the surface,” Dillon said. “The depths currently used for the underground injection of waste fluids do not store enough energy for a large-magnitude earthquake.”
“To date, only magnitude 4 and one magnitude 5 earthquake have been caused by the injection of underground fluids,” Dillon said.
The state oil commission, charged with regulating the industry, will update the earthquake working group on the situation in Colorado, commission director Matthew Lepore said.
“There’s not much of an update for us to give here,” he said. “We have a fairly detailed program, and if other states don’t have that, we obviously would want to share that sort of information with them.”
Lepore said it’s too early to tell whether the working group would lead to new state regulations on deep-injection wells. He is interested, however, in learning more about earthquakes that have occurred in other states, such as Oklahoma.
Stuart Ellsworth, a petroleum engineer for the state oil commission, believes the risk of earthquakes caused by wastewater disposal in Colorado’s deep wells is “very low.” The state closely regulates oil and gas wastewater wells in Colorado by limiting where the wells are located, the volume of water disposed and the kinds of rock formations where water can be injected.
“It’s a very detailed review,” Ellsworth said.
Steve Lynn can be reached at firstname.lastname@example.org and 303-630-1968 or 970-232-3147. Follow Lynn on Twitter at @SteveLynnBW.