In a new study, the U.S. Geological Survey shows an increasing correlation between Midwest energy drilling and earthquakes.
Michigan regulators already acknowledge that, in certain conditions, there is a link between these operations and minor earthquakes. WKAR's Mark Bashore spoke with Michigan's top energy drilling regulator, State Geologist Hal Fitch, about the study.
MARK BASHORE: This story involves hydraulic fracturing. “Fracking” as it’s called, pumps highly pressurized water, sand and chemicals into rock. Sometimes, it’s to dispose of waste water in waste wells. Other times it’s to get at gas and oil in drilling wells. Some environmental groups are extremely wary of the practice. Still, historically, fracking has gone on for decades in Michigan with only a limited number of minor tremors. The state continues granting new permits to drill every year.
Fitch believes the U.S. Geological Survey is a credible organization, but he says the report linking drilling to quakes doesn’t provide definitive proof.
HAL FITCH: What they have so far is a correlation. They haven’t really shown a cause and effect, but a high level of correlation. A high number of earthquakes in zones where there are injection wells---at least under those certain conditions—indicates there’s probably a connection there. It’s not definitive, but it probably is a connection.
BASHORE: According to NPR science reporter Christopher Joyce, the new data suggest an increase in Midwest tremors in recent years is tied not so directly to the hydraulic fracturing process itself. It links them to something else. Let’s listen to part of that report.
CHRISTOPHER JOYCE: Waste wells have been around for decades. In fact, there are tens of thousands of waste wells in the country, but very few quakes. But what’s changed is that the gas industry is using--and disposing of--more water. Waste wells are often deeper than gas drilling wells. They go in at the ‘basement’ rock where faults are more common.
BASHORE: Can I get you to respond to that please?
FITCH: Sure. We’ve known for many years that injection wells can trigger minor earthquakes. And there is quite a bit of correlation there, quite a bit of evidence that that may have happened.
You have to have a pre-existing fault, a zone of weakness in the earth’s crust with stress on that until it builds up enough pressure or enough stress to make that fault move. Now if you inject fluids near that, at a high enough pressure, it can lubricate that fault zone and cause some slippage that would have been delayed otherwise. So far, injection wells have only been associated with earthquakes of a minor magnitude that can just barely be felt. And we don’t believe there’s potential for them to cause major earthquakes that could cause damage.
BASHORE: Given that there are about 400 more permits per year going out though here in Michigan, does that change the equation at all?
FITCH: Those 400 permits are mainly for exploratory wells to produce oil and gas, not for injection wells. We do permit a few injection wells every year. We want to make sure there’s adequate capacity to dispose of the waste water that’s associated with oil and gas production. But again, we scrutinize every application for a waste water disposal well to make sure it’s not going to be---that it doesn’t have the potential to cause an earthquake or other problems, including contamination of the environment.
BASHORE: One seismologist at the University of Texas claims that decades of extracting oil and gas also can alter the local geology. Michigan has mined natural gas and oil for decades in a number of places. Should that be a worry?
FITCH: I’m not sure what he’s referring to in terms of altering the geology. Certainly when you produce oil and gas, you remove some of the fluids from the rock, but in the setting of Michigan, we have not seen any effect from that, from just strictly the removal of oil and gas, or for that matter, from the injection of waste water and we don’t anticipate that will see any in the future.