HUTCHINSON, Kan. (AP) — For at the last 15 months, Kansas geologist Rex Buchanan estimates, he's spent 90 percent of his time studying something once relatively rare in the state - earthquakes. He has learned a lot, said the director of the Kansas Geological Survey, whose focus in the past was primarily on water and geologic formations, including just how little is known, The Hutchinson News reports. One thing that has become clear, Buchanan said, is that there is a correlation between the majority of the 120-plus earthquakes recorded in Kansas last year and the injection of wastewater into deep disposal wells. "What's very difficult is to point to a specific earthquake and say a specific disposal well caused that," he said. "So, how to mitigate the earthquakes is what we're struggling to resolve." There has been consensus within the industry "since the '60s, if not before," Buchanan said, that pumping fluids into deep underground wells used to dispose of wastewater, also called waste injection wells, can trigger an earthquake.
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While disposal wells have been used by oil producers for more than 50 years without producing earthquakes, there has been an explosion in the number of those wells - and the amount of fluid being pumped underground - with expansion of hydraulic fracturing, or "fracking," for oil and gas recovery. The fracking boom followed the recent discovery that it's an effective method for tapping previously unrecoverable oil trapped in geologic shale formations found in certain U.S. locations, including northern Oklahoma and south central Kansas. In the fracking process, each production well requires between 1 million and 4 million gallons of water to fracture the rock and remove the oil or gas. The process contaminates the water, so it must be disposed of. "It's really easy to look at an earthquake swarm or even a single one, see a disposal well and say, 'That's the problem,' " Buchanan said. "But it may not be. It may be a low-pressure disposal well that's been putting water in the ground a long time. So you may go to the next higher volume well and say, 'That's it.' Proximity is a way to go about it, but it's not clearly the most efficacious way. It's not a simple thing," Buchanan said. Movement along faults or fractures in the subsurface of the Earth is what causes earthquakes, whether natural or induced. A fault must be present for there to be an earthquake, Buchanan said. Officials believe they know where some faults are in Kansas and Oklahoma, but not most.
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"The earthquake info you guys see is from the USGS National Earthquake Information Center in Golden," Buchanan said. "It's based on a national network. The three stations in Kansas don't allow us to get real good location accurately. The epicenters it puts out you may be able to move 4 to 5 miles. There's a lot of uncertainty." Over the past month, the state has purchased and located four temporary monitoring stations in south central Kansas, and plans are to set up two more. "The more monitoring is a good start," Buchanan said. "Really, it's the key. Ultimately we have to figure this out and we can't figure it out without monitoring. It's a good first step. What to do with that information is the next question."
