The top geologists in Colorado and Oklahoma, states with significant natural gas and oil resources, said researchers with the U.S. Geological Survey (USGS) were hasty in suggesting that injection wells used to dispose of wastewater from drilling operations are responsible for an increase in earthquake activity in the Midcontinent region.
Earlier this month scientists from the USGS earthquake research center in Menlo Park, CA, released an abstract stating they believed a six-fold increase in the number of earthquakes of 3.0 magnitude or greater since 2001 -- over 20th century levels -- were caused by an increase in oil and gas activity (see NGI, April 2).
"I think it's really premature," Vince Matthews, Colorado's state geologist and director of the Colorado Geological Survey, told NGI. He added that he and his counterparts "suddenly [started] getting all of these interviews regarding this abstract, which none of the other state geologists in the Midcontinent knew about. I think there are others that are concerned about these press releases and the validity of their conclusions."
Randy Keller, Oklahoma's state geologist and director of the Oklahoma Geological Survey, echoed that sentiment. "We consider a rush to judgment about earthquakes being triggered to be harmful to state, public, and industry interests," Keller said. "We are taking a measured and scientific approach to addressing issues so that any conclusion that earthquakes are linked to oil and gas activities can be scientifically defensible." Keller said it was important to remember that earthquake processes in the stable interior of continents take hundreds to tens of thousands of years to occur, yet meaningful earthquake monitoring has only been technologically possible for about 40 years.
One of the areas of increased seismicity USGS researchers have been focusing on is a coalbed methane field in the Raton Basin along the Colorado-New Mexico border, just west of Trinidad, CO. Matthews said there were stark differences between injections wells at Trinidad and at three other areas in the state: Paradox Valley, Rangely and the Rocky Mountain Arsenal.
"The wastewater that's being injected in Trinidad is not going in under pressure, as it was at those other locations," Matthews said. "That's a huge difference. The USGS also said that when the injections were stopped at the other locations, the earthquakes stopped. Well, the injections in Trinidad haven't stopped, they have been continuing at exactly the same rate. And yet the earthquakes did stop on that fault.
"There are these tremendous differences that, as a scientist, I don't like reading about in press releases. I want to see the theory and the data. I want to know if we can make conclusions that really make sense and are well supported by theory and by data. And there's a lot of good data that's being collected right now, most of it from the industry."
Last month Ohio regulators said a dozen small earthquakes in northeastern Ohio over the last year may have been triggered by a wastewater disposal well in Youngstown (see NGI, March 12). In 2011 Arkansas established a moratorium on wastewater disposal wells in an area of the Fayetteville Shale after similar quake activity was reported there (see NGI, Aug. 1, 2011).
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