Link between fracking and quakes unsure


A 4.0 magnitude earthquake near a Youngstown, Ohio, natural gas well on New Year’s Eve has invigorated the public debate on the safety of hydraulic fracturing.

Activists there and elsewhere, such as in the United Kingdom, have called for a moratorium on the fracking process, increasingly widely used to extract gas from shale rock. In response, energy company officials have said their wells may not be to blame for nearby earthquakes.

So is fracking a dangerous source of earthquakes that should be halted? Or is it harmless when it comes to quakes? Scientists say the truth is somewhere in between, but generally believe fracking poses manageable earthquake risks.

Scientists began to understand that humans could cause small earthquakes in the 1960s, when the U.S. Army drilled a 12,000-foot well at the Rocky Mountain Arsenal, near Denver, to dispose of waste fluids. This created a series of unusual earthquakes in the area.

Later that decade, at an oil field in Rangely, Colo., tests were done and seismologists found that changes in the number of earthquakes recorded per year correlated with changes in the quantity of fluid injected into the ground.

“It’s important to recognize that the association between injection and triggered earthquakes has been known about for about 40 years,” said Mark Zoback, a Stanford University geophysicist.

But that doesn’t necessarily mean that hydraulic fracturing poses a significant public threat.

There are, after all, about 50,000 injection wells in the state of Texas, and only a handful of earthquakes a year.

There are four steps to the fracking process, which energy companies use to extract natural gas from shale rock formations that are thousands of feet beneath the surface.

First the well is drilled, and then highly pressurized fluid is injected to break up the rock. This increases the rate at which natural gas can be produced from the well.

At that point something must be done with the wastewater used to frack the well. To avoid contaminating nearby groundwater, it often is injected back, deep into the well.

It is this step, scientists believe, that can trigger earthquakes.

Although the world’s strongest earthquakes occur along the major fault lines, there are smaller, pre-existing faults all over.

The injection of water can change the pressure along these faults, causing them to slip and triggering small earthquakes, scientists say. Fracking, then, might cause an earthquake sooner than it would have occurred naturally.

But the process seems unlikely to amplify a tremor.

“My preliminary studies suggest you almost never get induced earthquakes that are bigger than the natural earthquakes in an area,” said Cliff Frohlich, a researcher at the University of Texas at Austin’s Institute for Geophysics.

That was the case even with the Youngstown quake.

As recently as 1998, there was a magnitude 4.5 earthquake near the city, according to the U.S. Geological Survey.

Although scientists say they have a basic understanding of fracking and earthquakes, more research is needed to put further limits on the risk posed by the process.

“I think it’s a manageable problem,” Frohlich said. “To me it seems that, especially if more research were done, it’s possible to establish some areas of the country where you could do almost any amount of injection.”

And in those areas where wastewater injection might be a seismological threat, he said, there may be other disposal options.

For now, then, it’s probably the safest practice to carefully monitor large injection wells in tectonic regions, scientists say.

Researchers hope to identify and prevent a situation in which fracking might cause severe seismicity problems.

This can be done through better imaging technologies to look at subsurface rock formations, as well as other monitoring of fracking wells, said Robert Stewart, a University of Houston geophysicist.

“Experience, research and case histories are required to try to find any rare and possibly untoward circumstances where hydrofracking could be undesirable,” he said.

Eric Berger

20 Responses

  1. Howard S says:

    The headline is obviously intended to catch peoples attention and attract readership, but is completely unsupported by the content of the article. The uncertain “link” to earthquake activity near Youngstown is related to fluid injection in disposal wells located in Ohio, not the hydraulic fracturing of new production wells in Pennsylvania. Apparently this distinction is not understood by the majority of readers and the writer as well.

    Injection wells have been employed for decades to dispose of produced water from conventional wells and more recently flowback from unconventional wells. The volume of produced water disposed through injection is at least an order of magnitude greater than that generated by hydraulic fracturing.

    The media has an obligation to do a better job of research. Adding to the current oversupply of misinformation on fracking is not in the public interest. A well researched discussion of the issues surrounding induced seismic activity from the disposal of fluids in injection wells is what is needed. If anything, the current concerns about induced seismic activity from injection wells should be stimulating a dialogue about the opportunities to treat these contaminated waters so they can be beneficially reused rather than disposed through reinjection.

  2. JohnD says:

    Stephen, the delay between the injection and the final events was due to the diffusive nature of the process. Water does not flow instantaneously; instead, it takes time to reach further away. As a result, the pressure near the well can be quite different from that near the fault. And an earthquake can only happen once the hydrostatic pressure near the fault is high enough.

    This has been seen numerous times, from the Rangley experiment to the Monticello dam failure. The deeper and further from the water source the fault is, the longer it takes for the pressure pulse to work its way down (and the smaller the final pulse is).

  3. There are underappreciated facts about the Denver Rocky Mountain Arsenal #3 well. It was drilled to about 12,700′. It is reported by Dr. Major of Colo School of Mines in 1977 that it was the only time the call “Loss of Circulation” was greated with cheers on the rig floor. That well took about 165,000,000 gallons of disposal water from about 1965 to 1967. During this period, North Denver (Broomfield) experienced a growing number of quakes in the Magnitude 2.5 to 4 range. The Colorado government had the well sealed. This is the story most have heard.

    Where I think the story gets most interesting is that about 6 months, 11 months, and 18 months AFTER the well was sealed, Denver experienced its three biggest quakes: Magnitude 5.1, 5.3 and 5.5. These were shallow (5 km) and within a few miles of the well. The activity then declined. (This can be verified on the USGS Earthquake Archive)

    That the biggest quakes occured months AFTER the injection stopped is I think key to understanding the mechanism. Thermal contraction and expansion might play a part as well as pore pressure changes.

  4. JonC says:

    Do you even realize that the gas well near the earthquake had nothing to do with fracturing? It was an injection well.

  5. steve says:

    Ban heating oil and there ya go!

  6. JohnD says:

    David, your question is one that we seismologists get a lot. And the answer, surprisingly, is “No; we are better off with one big one”. The reason for that is because of the amount of energy in an earthquake.

    A magnitude 8 earthquake has the same amount of energy as 33 magnitude 7 earthquakes or 1,000 magnitude 6 events or 33,000 magnitude 5 tremblors. To put it in practical terms, let us suppose that you live in an area where there is a magnitude 8 earthquake every 99 years. In order to release enough energy to avoid that earthquake, you’d have to have a magnitude 7 every 3 years, or a magnitude 6 every month, or a magnitude 5 every day, or a magnitude 4 every 45 minutes. Needless to say, it is much simpler and better to simply prepare for that magnitude 8.

  7. David Gower says:

    Is it possible? If earthquakes are the release of tension between tectonic plates or cracks or fractures, is it possible that many small releases are better than that tension or pressure being released all at once in a bigger earthquake? Maybe there would be some beneficial effects if fracking does cause some small earthquakes.

  8. steve michalak says:

    fracking and drilling near the Youngstown area is just beginning because in the last year or so, that area down the Ohio River is believed to have the worlds largest shale deposits (produced Natural Gas) and the area has been hit by terrible economic woes the past 25 years.
    There is hope in Fracking/drilling there and a possiblilty of 100 employment in that area in the next 5 years.
    It is not going away.

  9. BigO says:

    a pragmatic response to Nicole – you obviously don’t believe what you hear from the oil industry, but I would also encourage you to DO SOME ACTuAL RESEARCH and not believe anything you hear from the anti-oil groups.

    Of specific note to you comment, one of those Oklahoma earthquakes you mentioned was centered thousands of feet BELOW where any fracking could have been going on. No association!
    So if you read something saying that those earthquakes were both caused by fracking then you can with a high degree of certainty infer that the author didn’t do his/her homework.

    So not to say that fracking, along with water wells for drinking water, can’t cause minor earthquakes, but the science does not support the “proof” that the anti-oil folks say they have.

  10. Locked says:

    Fracking does not cause earthquakes, it just makes your drinking water taste bad.

  11. Trail_Tramp says:

    JohnD knows where of he speaks. Here is a website for the US Department of Energy and Lawrence Berkeley National Laboratory on the subject of Induced Seismicity.

  12. Trail_Tramp says:

    As the experts say, it is the injection process not the fracing process which can cause small earthquakes and most of the injection wells are for the disposal (or recycling, if you will) of saltwater from the production of oil and gas…NOT of fluids from frac job flow back.

  13. Recon dad says:

    Fracking is to earthquakes as Obama is to jobs…..

  14. Dollar says:

    I don’t see how you can say that hydraulic fracturing causes quakes, it does not. Injection wells cause quakes.

    And there are all types of injection wells nationally. They are highly regulated by the EPA working through the states.

    The flow back from hydraulic fracturing can be dealt with in other manners, than injection.

    The fracturing of oil/gas shale formations does not cause quakes.

  15. txloanguy says:

    Temperatures raise – blame oil carbons. Economy – blame Bush. Earthquakes – blame fracking.

  16. Jimmy says:

    Of course, these drillers will not associate fracking with earthquakes. Do you think they’re stupid enough to sacrifice the fortune they would get if they say otherwise?

  17. Tricia says:

    More Environmental BS.

  18. JohnD says:

    I’ve done a lot of work on induced seismicity (that’s “man-made earthquakes” to those who don’t speak science). Right now, it appears that most of these quakes are not caused by fracking. My rationale is spelled out here:

    The short version is that the events are too large, too far away from the fracking, and move int he wrong direction. That isn’t to say that oil production cannot create earthquakes; Segall wrote a series of very convincing papers on that topic. But those are typically caused by withdrawal of hydrocarbons over a long period of time, not by the injection of fluids. (Full disclosure: I work for an oil company. They are in no way responsible for my views on this topic.)

  19. Nicole says:

    Another words, yes it causes earthquakes. Texas facts are going to be biased here. Fracking is big money and Texas is all about oil, at all costs, and without consideration of our environment and drinking water. The fact that they aren’t denying the possibility tells me all I need to know. They are injecting potent chemicals into the ground. When you think about this you know damn well we are drinking contaminated water, or will be in the future.

    Both recent earthquakes in Oklahoma happened at the same time they were fracking. It would a lie to deny the two incidences are related.

  20. Terry says:

    Don’t frack it, don’t ship it, don’t truck it, don’t pipe it, and don’t drill for it. And these morons will be the first to complain when the price of gas goes up.