Its been quite awhile since we checked in on the seismicity in Oklahoma. As we’ll see, on the whole the news is good, but there are a couple of things worth watching…
First, the number of quakes has steadily dwindled…
This is what you’d hope to see with decreases in wastewater injection. Some of this is regulatory, but a big piece is because the low price of oil made the more water-rich (an thus injection-heavy) fields less attractive.
If instead we look at seismic moment, things are somewhat less clear:
Now first off you see the big drop in increase of seismic moment starting in late 2016; that rate has continued to the end of 2018 (the red curve is new since the last post). But curiously it hasn’t dropped: the M4.6 in April of 2018 offsets the seemingly slowing rate since then–a straight line from the end of 2016 through early 2018 projects right to where the cumulative seismic moment stood at the end of 2018. At present it seems the moment release rate is pretty constant. For this to coexist with a decreasing number of earthquakes means that earthquakes are getting larger even as they are less frequent.
What this means is that while things are a lot better, they might not be improving as much as you could hope.
GG stumbled across a Factcheck.org posting on a run in between Oklahoma Attorney General and EPA director nominee Scott Pruitt and Senator Bernie Sanders over induced earthquakes in the state. The Factcheck.org piece does a really nice job of laying out the issues with the Oklahoma earthquakes (it is one of the finer discussions outside the professional literature–and more comprehensive than most of the academic papers).
In a sense, Sanders was implying that earthquakes are somebody’s fault and so there should have been legal action by the state. That’s not typically how this works; the state of Oklahoma does now regulate how injection companies can operate through their Corporation Commission (Colorado does it through the more narrowly focused Colorado Oil and Gas Conservation Commission). One would only expect the attorney general to step in if companies decided to defy government orders (which, at times, some injectors have threatened to do).
What does the EPA have to do with this? There are exemptions in federal law to allow most oil and gas operations to continue without interference, but it does seem the EPA has felt that it has a role to play with injection wells. More traditionally, the EPA has kept an eye on surface disposal of industry wastes and has taken a greater interest in the release of methane from natural gas production and pipeline facilities. So presumably Sanders and others asking about the earthquakes were sniffing about seeing if Pruitt was likely to pull the EPA back from oil and gas production oversight. This might be the highest profile seismology has ever had in confirming cabinet positions.
Well, it appears that the state of Oklahoma finally bought into the connection of earthquakes to deep injection wells as the recent M5.6 earthquake led them to shut down injection wells in the vicinity of the epicenter [and once again we learn the national media still cannot discern between fracking, which is not the cause here, and injection of waste water, which is the likely culprit]. Interestingly, there are two views on how Oklahoma seismicity is varying: Dan McNamara of the USGS argues that seismicity is still on the rise, while Oklahoma Geological Survey director Jeremy Boak is quoted by the Tulsa World that “I still expect to see declining figures over the rest of the year just because we’ve decreased the (wastewater) injection so much.”
Given how long the Oklahoma survey dragged its feet on acknowledging the problem, their credibility is kind of at a low point. McNamara in November said that more M5s were likely, and two more have happened since. McNamara made a plot of seismic moment over time that is pretty damning:
The big decrease in seismicity Boak was excited about is the somewhat shallower slope of moment increase in early 2016, a decrease now obliterated by this latest quake.
The problem is that fluid injection of this magnitude over this amount of time has probably not reached any kind of equilibrium yet. The overall upward concavity of this plot suggests that we aren’t at the end of increasing rates of moment release. Hopefully it will come as a boatload of small-impact M4s and low M5 events, but M6 events don’t seem implausible. If you look at a much smaller example, the likelihood of earthquakes continuing for decades is substantial–even if injection stops.
Back in the 1960s the Army injected wastewater at the Rocky Mountain Arsenal into basement. This caused a bunch of earthquakes and eventually the injection was stopped–but two years later some of the largest quakes in the sequence happened. At the time the interpretation was that the pressure wave from the injection was propagating outward and so could have a substantial time lag. Regardless of mechanism, it should concern Oklahoma residents that in a similar case with much, much smaller volumes of water being injected that earthquakes continued long after injection ceased.
It is great that the Corporation Commission in Oklahoma has acted to shut down a number of injection wells. Too bad some of this didn’t come before the billions of barrels of produced water were injected into the Arbuckle Formation. We will see if this closing of a barn door caught the horse or not. The problem may be that the pasture gates need closing too: the production of oil is not likely to shut down at the same rate as injection well capacity; produced water will probably be rerouted to wells that have not yet been shut down. And while many wells probably pose no risk of inducing earthquakes, some probably do. So this might simply migrate the problem even farther afield.
One reality is that the duration of time needed to really see if this helps–probably on the order of years at this point–is almost certainly beyond the ability of government overseers to keep operators from applying political pressure to resume operations at some level. The only really good solution is some kind of processing of these waters so they can be released at the surface, but such purification is expensive and would require creation of infrastructure that doesn’t yet exist.
Well, of course, there is another solution: quit pumping oil. Don’t hold your breath wait for that one. And if you live in Oklahoma, you might just want to see how much that earthquake insurance is. And find those webpages Californians have perused for years on how to make your house more quake-proof.
A M3.4 earthquake in Greeley, Colorado is pretty suspicious. The news report has the odd sentence
Earle [of the USGS] said earthquakes like this have been caused by underground disposal of fracking waste water, but it is far too early to determine if that was even going on in the area of the earthquake.
Um, this actually isn’t so hard to determine (one wonders if anybody looks at the Colorado Oil and Gas Commission databases to at least know where there are disposal wells). The answer is yes, there are disposal wells in the vicinity, and given the history of the region, the previous experiences with deep injection producing earthquakes in the Front Range of Colorado (see below), the odds are quite high that this was indeed induced by deep injection of production (used in fracking) water….but at present the location is pretty poor and you’d like to see the injection histories of nearby wells…
Update: the Greeley paper ran a story on a quick RAMP (Rapid Array Mobilization Program, otherwise known as Run Around with Much Panic) deployment of seismometers run out of CU Boulder to better locate earthquakes in the area (the locations reported of the 3.4 used stations no closer than 70 km away). They followed that up with an unusually comprehensive story about wastewater disposal.