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Why some fracking wells are prone to triggering earthquakes
Some of the biggest fracking-induced earthquakes in the world — including three higher than magnitude 4.0 that could be felt by humans — have taken place in the Kaybob Duvernay Formation near Fox Creek, [Alberta]. But they've happened only in certain areas and only since 2013, even though fracking began there in 2010. Why?
A study led by Ryan Schultz, a seismologist with the Alberta Energy Regulator and a geophysical research scientist at the University of Alberta, shows that the underlying geology determines whether earthquakes can be induced at all by a particular well. But if an earthquake can be induced, then the number of earthquakes increased with the amount of fluid pumped into the well, reports the study published Thursday in the journal Science [DOI: 10.1126/science.aao0159] [DX].
The authors of the study, which also involved researchers at Western University, the University of Calgary, the University of Alberta and Natural Resources Canada, came to that conclusion after analyzing drilling records for around 300 wells in the region submitted to the Alberta Energy Regulator. They found that the reason earthquakes didn't start there until 2013 was because companies didn't start drilling earthquake-prone wells until then.
So what makes a well earthquake prone? Earthquakes happen at faults, where two of the Earth's tectonic plates come together. Earthquakes occur when the two plates slip or slide relative to one another. In order to cause an earthquake, a fracking well needs to have a physical connection via the underlying rock to a fault that is oriented so that the pressure of fluid from the well can change the stress on that fault and increase the chance of it slipping.
Also at the University of Alberta.
(Score: 3, Interesting) by Adamsjas on Monday January 22 2018, @02:53AM
Its long been argued back and forth for decades that a consistent patter of little earthquakes forestalling a big one.
Modern geologists insist this theory first proposed in Richter's day is wrong, and usually provide wandering arguments about total energy to support their claim: https://www.quora.com/Do-small-earthquakes-prevent-occasional-larger-ones-from-occurring [quora.com]
Yet A dearth of observations of larger earthquakes on the world's many creeping faults suggests the modern guys are missing something pretty big. They only study large quake areas after all.
It can't be proven one way or the other because there has been no way to test the theory other than statistical guesswork.
Problem explained here back in 2007:
https://phys.org/news/2007-03-scientists-source-mysterious-tremors-emanating.html [phys.org]
I think Frojack's suggestion in his first post suggests an experiment.
You could drill, (but not frac) into an fault that you had reason to believe was locally locked. (This condition can be detected with seismographs.) You could wait a year or two, then frac those same wells, attempting to unstick that locally locked zone.
If that induces small quakes locally as well as in both directions along the fault you have some evidence that YOU may have prevented or delayed the big one by allowing the whole fault to shift just a little. Or you might get sued to bankruptcy.
Note that Frojack isn't the first to suggest this.
It was a topic for a while in 2004, where the US Army discovered pretty much the same thing that this Canadian paper proclaimed. And use of injection wells was suggested back then as a quake inducing tool.
http://www.nbcnews.com/id/6759689/ns/technology_and_science-science/t/can-earthquakes-be-tamed/ [nbcnews.com]
http://www.nbcnews.com/id/6759689/ns/technology_and_science-science/t/can-earthquakes-be-tamed/ [nbcnews.com]