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Oil Addiction, Not Fracking, Caused the 2011 Oklahoma Earthquakes

The views expressed are those of the author and are not necessarily those of Scientific American.


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Earthquakes in region of Prague, Oklahoma, from Nov. 5, 2011, through Dec. 4, 2011. Red indicates 2.2 magnitude, up through magenta representing the 5.6 magnitude quake. Credit: Flickr/KellyMcD

Earthquakes have become more than 10 times more common in normally quiescent parts of the U.S., such as Ohio and Oklahoma, in the past few years. Given the simultaneous uptick in fracking—an oil and gas drilling technique that involves fracturing shale rock deep underground with the use of a high pressure water cocktail—it’s common to suspect a link. There might be one, but the real culprit behind the largest earthquake in Oklahoma’s recorded history is not what goes down but what comes up with the oil: wastewater.

Oklahoma has long benefited from a robust oil industry. One of the side effects of oil production is that a lot of water flows back to the surface with the petroleum. That flowback water must be disposed of, because it is laced with all kinds of contaminants the liquid solvent has picked up during its long residence deep underground, ranging from trace amounts of radioactive elements to lots of salt.

In Oklahoma and in much of the rest of the country, the most common burial ground for such wastewater—whether we’re talking oil or gas—is a disposal well back underground. Oil producers in central Oklahoma had been using this approach for 18 years when a swarm of powerful earthquakes rumbled across the countryside starting on November 5, 2011. The biggest temblor, a magnitude 5.7 felt as far away as Milwaukee, was linked to pumping yet more wastewater down old oil wells in the vicinity. (The wastewater pumping there continues despite the quakes.)

According to a new study published online March 26 in Geology, the earthquake was indeed caused by filling up the old oil cavities with water until there was simply too much pressure on the surrounding rock. Records showed that after years of requiring little pressure to dump the wastewater, oil operators recently have had to actively pump the water down the old wells to overcome a more than 10-fold increase in underground pressure, which peaked at 3.6 megapascals, or 525 pounds-per-square-inch. That’s because the volume of wastewater pumped down had exceeded the volume of oil extracted, suggests the team of researchers from the University of Oklahoma, Columbia University and the U.S. Geological Survey. That increased pressure then caused the rock to jump along a pre-existing fault, known as the Wilzetta Fault.

Similar wastewater quakes have struck from Ohio to California—and abroad in the past few decades. And with the rapid expansion of fracking for oil and natural gas for  contributing an ever-growing volume of wastewater, unregulated dumping down disposal wells could lead to similar quakes elsewhere unless new treatment methods can be found. Or oil and gas operators could be required to avoid dumping near known faults. Operators also could provide a record of fluid volumes and the pressures they encounter deep underground—a potential warning sign. If the new research is correct, the earthquake near Prague, Okla., now stands as the largest earthquake ever recorded as a result of fluid injection.

And the Wilzetta Fault remains under pressure from local dumping despite the recent earthquake, which buckled pavement and destroyed 14 homes. Our fossil fuel addiction means there’s a lot of wastewater to get rid of and a lot of questions about whether it can be safely dumped underground.

David Biello About the Author: David Biello is the associate editor for environment and energy at Scientific American. Follow on Twitter @dbiello.

The views expressed are those of the author and are not necessarily those of Scientific American.





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  1. 1. David_Bressan 3:15 pm 03/27/2013

    Fluid Injections and dam constructions are in fact know to generate shallow earthquakes, but this statement by the Oklahoma Geological Survey seems to disagree with the results of the paper http://www.ogs.ou.edu/earthquakes/OGS_PragueStatement201303.pdf

    Link to this
  2. 2. Sisko 3:30 pm 03/27/2013

    David Biello

    Isn’t the Oklahoma Geological Survey a less biased source of information than LDEO?

    Link to this
  3. 3. josephcraig 3:41 pm 03/27/2013

    Another article side stepping personal and corporate greed and blaming “addiction”. That and not “addiction” is the core cause and the addiction is a corporate profit fueled and sponsered symptom!

    Link to this
  4. 4. jtdwyer 4:13 pm 03/27/2013

    It’s important to understand as much as possible about the conditions that produced the quakes, but the bottom line is that fracking activity produced the quakes!

    Unless fracking can be accomplished without the risk of producing earthquakes (my impression of the companies carrying out fracking activities is that they are neither closely regulated nor self-regulated) fracking activities are likely to produce earthquakes.

    Oklahoma may have been largely pumped out already, but there have also been earthquakes closely associated with fracking in central Arkansas and, I think, many other areas. It should be obvious that the expensive fracking process is mostly used to recover residual oil from reservoirs, large and small, that have previously been practically depleted – so unless some reliable method of avoiding overpumping can be employed if the field, earthquakes will remain a risk.

    There are several really dangerous mid-continent faults in the U.S., particularly the New Madrid fault in the ‘boot heel’ of extreme south-east Missouri and north-east Arkansas. Hopefully fracking activities won’t one day induce a truly catastrophic earthquake…

    Link to this
  5. 5. sault 4:31 pm 03/27/2013

    Sisko,

    Nope. A lot of times, many state-level regulators or the politicians that decide their staffing are bought off by the corporations they’re supposed to regulate.

    Link to this
  6. 6. Sisko 4:59 pm 03/27/2013

    sault/David

    Doesn’t the headline “Oil Addiction, Not Fracking, Caused the 2011 Oklahoma Earthquakes” seem rather biased given the Oklahoma Geological Survey’s conclusions and the fact that LDEO concluded nothing definitive?

    David’s headline assumes a conclusion unsupported by the LDEO or the Oklahoma Goelogical Survey.

    Link to this
  7. 7. alan6302 5:53 pm 03/27/2013

    Has anyone debunked the nuclear explosion theory for DC.

    Link to this
  8. 8. hamo-1 6:42 pm 03/27/2013

    “The views expressed are those of the author and are not necessarily those of Scientific American.” – so under the banner of ‘blog’ or ‘observations’ the SA writers or contributors are not bound to data or conclusions such as those provided by the OGS in this case. So in the realm of mere speculation, one could also opine that waste water pumping may benefit the area by providing a lesser release of stored energy from a fault rather than a potentially higher release had nature built up more pressure over a longer time period, thus resulting in less damage to human-made structures than a natural event. The waste water doesn’t (and can’t) generate the earthquake forces, it just provides a mechanism for release. — It’s all speculation (or expression of an agenda) without supporting data and science based on those data.

    Link to this
  9. 9. David Biello in reply to David Biello 8:35 pm 03/27/2013

    That’s right David et al. OGS released its own statement disputing the finding and giving its own reasons for believing the quake to be “natural,” mostly premised on 3D seismic. But most of the other geologists I’ve chatted with found the LDEO (and USGS and University of Oklahoma) result robust and convincing. Take a look for yourself, the link to the study is in the post.

    Of course, it’s still open for debate. But as for the headline, wastewater disposal from the oil industry is posited as the direct cause of the 2011 temblors near Prague. If you accept that conclusion (and I know some of you don’t) then the headline follows. Hope that clarifies.

    Link to this
  10. 10. phalaris 3:11 am 03/28/2013

    David Biello -
    thanks for an interesting and informative overview.
    And, to me right now, it seemed balanced: geo-energy and irrigation can also be to blame as well as oil and gas fracking.

    Everyone can take their own message home. Rather than knee-jerk cries of corporate greed, it’s more honest, in my opinion, to see as us and our expectations as the prime mover.

    Link to this
  11. 11. sunspot 3:14 pm 03/28/2013

    “oil operators recently have had to actively pump the water down the old wells to overcome a more than 10-fold increase in underground pressure…That’s because the volume of wastewater pumped down had exceeded the volume of oil extracted.”

    It’s hard to believe that the oil operators didn’t stop pumpimg when the pressure increased sharply. The increase in pressure is not likely to directly cause the quake, but forcing an oil/water mixture through porous rock near a fault zone will lubricate the fault, and lead to slippage. This is exactly the same issue with fracking causing quakes.

    Perhaps a majority of readers have a problem with the headline of this post because of the similarity to fracking and wastewater dumping. If an OGS report exonerates the oil companies, in a state that is synonymous with big oil interests, then the OGS has a credibility issue that should be addressed by independent scientists. Otherwise the report will just be dismissed by most readers as politically influenced.

    Link to this
  12. 12. jtdwyer 3:29 pm 03/28/2013

    David Biello,
    One of us is misunderstanding the relationship between fracking and waste water pumping, and earthquakes.

    The ‘LDEO’ study states:
    “The recent boom in U.S. energy production has produced massive amounts of wastewater. The water is used both in hydrofracking, which cracks open rocks to release natural gas, and in coaxing petroleum out of conventional oil wells. In both cases, the brine and chemical-laced water has to be disposed of, often by injecting it back underground elsewhere, where it has the potential to trigger earthquakes.”

    The issues that are associated with ‘fracking’ also exist for pumping water into depleted wells to extract residual oil. It is both activities that produce the waste water that is being disposed of by pumping it back underground. Even if it is considered to be an indirect cause, the waste water pumping is a direct byproduct of fracking activities.

    The studies do not absolve those using ‘fracking’ from causing earthquakes!

    Link to this
  13. 13. Gaythia 5:51 pm 03/28/2013

    Buried near the end of the article, the author himself states:
    “And with the rapid expansion of fracking for oil and natural gas for contributing an ever-growing volume of wastewater, unregulated dumping down disposal wells could lead to similar quakes elsewhere unless new treatment methods can be found.

    The fact that the earthquakes are not caused by hydrolic fracturing for natural gas or pressurization for oilfield enhancement, but rather by the disposal of the wastewater produced as a direct result of those procedures seems like a bit of a technicality.

    As jtdwyer says above: “The studies do not absolve those using ‘fracking’ from causing earthquakes!”

    Link to this
  14. 14. Profpeterstyles 4:45 am 03/29/2013

    However only a minute fraction of the waste water wells in the US, of which there are many thousands generate felt seismicity, and so it is most important to understand why these handful of wells do. That means determining whether they are interacting with specific faults or fault systems. The magnitude of the seismicity appears to be correlated with the total volume of water injected and has grown with time and may be a case of the Kaiser Effect which is where a rock stressed to a certain level will NOT generate acoustic emission ( microseismicity) until it is restressed to a level greater than it has previously experienced.

    It is completely meretricious to link the actual fracking process which involves a short duration injection of a limited volume of water ( yes, limited… the volume is equivalent to a single irrigation of a reasonably sized farm field) to long-term high volume waste water disposal. We have known since the 1960s ( Rangeley Well Colorado) that waste water injection can in certain circumstances generate seismicity and it is incumbent on us to try to understand this better.

    In all hydrocarbon activities which involve either the withdrawal of reinjection of fluids of any kind ( including by the way CO2 sequestration) it is the geology which is the controlling factor and it is through a thorough investigation of structures and stress tensors using the already available seismic technologies which will mitigate these issues.

    Link to this
  15. 15. Dr. Strangelove 2:04 am 03/30/2013

    David Biello

    I doubt waste water injection is the cause of Oklahoma earthquakes. Fluid injection can cause earthquakes if it is forced under high pressure. In oil waste water, you don’t need to force it because the water came from the same cavity. Minus the oil, the cavity is larger than the volume of waste water.

    Your quoted pressure of 3.6 MPa is low. The hydrostatic pressure in a 6,000 ft oil well is 17.9 MPa. If they only got 3.6 MPa, that’s a shallow well 112 ft deep.

    BTW, the rock permeability will increase and pressure decrease, if you inject water because the rocks at 6,000 ft is about 5C warmer than ambient surface water temp. The rocks will contract and the fissures will open wider upon contact with cooler water.

    Link to this
  16. 16. Dr. Strangelove 2:18 am 03/30/2013

    I should know. We’re hydrofracturing at 9 MPa forced injection and we’re only getting micro earthquakes too small to be felt. We never had any big earthquake in 10 yrs.

    Link to this
  17. 17. G. Karst 12:07 pm 03/31/2013

    Isn’t it possible that such micro-earthquakes may be relieving fault stressing? Could it be such activity and quakes are saving us from the “big” one? Some research in this area, may give us a tool. GK

    Link to this

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