How definitive would you have to be…

…to know when earthquakes are caused by an injection well?  In Greeley, increased volumes and pressures at a well were nearly immediately followed by earthquakes at and below the well that increased in size until one was felt.  When the well was shut down, seismicity backed down.  As the well was returned to service, some seismicity recurred.

According to the Colorado Oil and Gas Commission as reported in the Denver Post, this indicates that

any connection between the Greeley quake and the injection well remains in the “not definitively caused by” category

GG notes that such a close temporal and spatial correlation would put the well in the “almost certainly the cause of seismicity” category.  Evidently science speak and lawyer speak use words differently.

While COGC speaks with forked tongue to avoid alienating the oil and gas industry, they have acted quite responsibly in this matter, especially compared with some other organizations farther south.  

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5 responses to “How definitive would you have to be…”

  1. honeymustardseeds says :

    The well didn’t *make* it quake, it very well could have been waiting to go off at any moment! Therefore, the well merely assisted, but didn’t directly cause it. Plus, we’re not down there so we can’t actually *see* what’s making the quakes happen!

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    • cjonescu says :

      Sorry, that is pretty improbable. If the area was dangling on the edge of failure where an earthquake was imminent you would expect to see background seismicity in the region, which we do not, and it would be quite the coincidence for this well to have been drilled to where the quake would happen (there are not that many injection wells in Weld County yet). Plus tectonic earthquakes tend to be deeper (5-25 km down). Now it is true that the stresses that drive the failure were (most likely) not generated by the injection of waste fluid but the fluid drove the failure envelope towards the conditions that existed.

      As for not seeing what is down there, well, all geophysics is that way and yet, curiously enough, geophysics is good enough to reveal where oil, gas, and metal deposits are (not to mention plumes of groundwater contaminants, salt water incursions, archeological sites, etc.). The way we determine what is going on is by developing conflicting hypotheses and focusing on observations that would distinguish between them. If this were a matter of pure science nobody would be pursuing this any farther, but because company incomes and people’s jobs are involved, there is push back. Ideally you would monitor seismicity before an injection well was placed and continue monitoring through its operation. In general, when you see spatially and temporally associated seismicity with a well’s operations, you are pretty sure that the well is the culprit, and that is the case here.

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  2. cjonescu says :

    Ah well, your sarcasm is nearly verbatim what many in the oil and gas community are saying about these earthquakes, hence my misreading your tone.

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