Tag Archive | induced seismicity

Fracking Crossroads

It’s been awhile since we visited fracking.  As a reminder, fracking is injecting high pressure fluids into rock to break open fractures for oil and/or gas to migrate into the well; however, the term has been converted in popular culture to more or less be synonymous with oil and gas development in general. This misappropriation has largely been because of renewed oil and gas development fueled by the application of horizontal drilling into “tight” source rocks that have to be fracked to produce petroleum. (“Tight” formations are usually the source rock of petroleum but lack the porosity for the fluids or gas to migrate into a traditional reservoir; these are usually shales). You could just as well call it “horizontal drilling” as “fracking” and remain exactly as accurate.

GG has argued that fracking (senso stricto) itself isn’t nearly the problem; most of the complaints really come from having industrial activities (with associated noise and air pollution) near residential areas along with occasional failures of the packing of the well that can release drilling fluids or produced water into shallow aquifers. The other hazard that developed is the huge increase in produced fluids (the foul waters that accompany oil and gas development) that are usually disposed in injection wells, which has led in some places to pretty considerable increases in earthquakes, most notably in Oklahoma.

But as more and more operations are active, we’re seeing more incidents of the rarer side effects of fracking itself, in this case earthquakes generated by fracking activities. The most recent case is in England, where the sole fracking operation in the country now is at a standstill after producing a M2.9 earthquake.  Although it isn’t entirely clear whether there is a separate injection well in this system, it does seem from the reports online that this was caused directly by fracking. Following fracking induced events in Canada, Ohio, and Oklahoma, it seems that this worry can’t be entirely anticipated but can be managed by being ready to stop. In England, though, this might mean the end of attempts to use fracking to develop tight oil and gas in that country.

In the U.S., several Democratic candidates have called for an end to fracking, generally with little clarity of what exactly that might mean.  For instance, Elizabeth Warren tweeted out that she would “ban fracking- everywhere” on her first day in office (um, no, not a power the president has).  However, fracking is not mentioned at all on her rather meaty website, suggesting that her program might be a bit more nuanced than her tweet, but the rationale for at least some of the candidates is to end oil and gas development as a means of addressing climate change, which is a more scientifically literate reason for opposing all new development.

But one should be careful in these matters.  While we certainly need to leave a lot of carbon in the ground (barring a major success in CO2 scrubbing from the atmosphere), one would want to make sure that, say, banning fracking in areas where the technique is well developed not lead to new conventional development in fields presently untouched.

The British experience, though, is suggesting that exporting the U.S.’s success in tight oil and gas development might not go as smoothly as many in industry had hoped. Whether that is a good or bad thing depends on your perspective.

Is Oklahoma Now OK?

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.

If you want to see some reporting on how others view this, Tulsa World had a good end-of-year review. The data used here is from the USGS’s earthquake catalog.

All quiet on the plains…

Its been awhile since Oklahoma earthquakes made news and so it seems timely to look in on the Sooner State to see how things are going.

Last we looked in, numbers of earthquakes were down but the moment release was still pretty high. Predictions from Stanford late last year were that the decreased injection of wastewater would lead to a decrease in earthquakes over the succeeding five years. The USGS, in contrast, has continued to note that the decrease in the number of events does not mean a decrease in damaging earthquakes.

So far, the news is good.  Not too surprisingly, the number of earthquakes continues to drop:


So that continues the trend from 2016.  What about moment release?  Well, given the absence of news reports, you’d guess there is a decline there, too, and you’d be right:


And, indeed, 2017 has been dead quiet moment-wise as well.

Does this mean that the seismic risk is now gone?  Well, no.  That M5.7 earthquake in late summer last year was on an unrecognized fault.  The fluids migrating in the basement could encounter another critically stressed fault and trigger a significant earthquake. But for now, this is good news for Oklahoma residents.

Oklahoma Yin Yang

With 2016 coming to a close, GG thought we might want to see just how things are shaking out in Oklahoma, home of the great induced earthquake experiment. And there is something for everybody, depending on how you want to look at it.

For the optimists hoping that Oklahoma’s actions to slow wastewater injection will end the plague of induced earthquakes, we have plot number one: number of quakes with a magnitude of 3.0 or higher by month:


Earthquakes within Oklahoma, by month, 2016, from U.S. Geological Survey

The rate of such earthquakes dropped from nearly 4 a day in January to about one a day this month. And you could hope that this had something to do with this:


Monthly averaged daily injection volumes of Arbuckle disposal wells in the Area of Interest for Triggered Seismicity, from Oklahoma Corporation Commission, Oil and Gas Division. (December decline probably because of incomplete reporting).

The 25% reduction during the year in the rate of injection in the area where triggered seismicity has been observed might be responsible for this.  But there are other things to watch as well.  First, these are still pretty high volumes of water going back into the Arbuckle, and all the water that went down earlier is still making its way through the subsurface.  Second, presumably a lot of produced water is going to other wells, either in the Arbuckle outside the area of interest or into other formations. Third, a decrease in the number of M3+ events is not the same thing as a decline in seismic moment:


Seismic moment release in Oklahoma in 2016, derived from USGS catalog.

The 9/3/2016 M5.8 Pawnee, Oklahoma earthquake put a big damper on any celebration of a decrease in seismicity. The overall moment release of 7.8 x 1024 dyne cm is the largest single year moment release in Oklahoma history. As we noted before, this isn’t unexpected: the Rocky Mountain Arsenal sequence in the 1960s produced its largest quakes after the injection ended.

So we enter 2017 on a note of caution.  If you bought earthquake insurance in Oklahoma, don’t let it lapse just yet. You might get shaken a bit less often, but when you do get a quake, it might still be pretty big.

P.S.: there are a couple of nice visualizations out there.  Tulsa World put together an interactive map a year ago showing how produced water injection was varying over time and by county. The Oklahoma state government has an interactive figure with recent earthquakes and disposal well locations.

Oklahoma Dreamin’

Back in September, Oklahoma had a M5.6.  Some of you might recall the difference in opinion between USGS scientist Dan McNamara, who expected continued seismicity, and Oklahoma Geological Survey director Jeremy Boak, who said “I’d be surprised if we had another 5.0 this year.”

Well, Director Boak hopefully was in the vicinity to be surprised in person by the M5.0 today that damaged buildings in Cushing, OK, site of the largest oil storage facility in the country (which at least apparently escaped any damage). Yeah, once more wishful thinking trumped by actual scientific examination….increasingly it seems the branch McNamara has climbed out on is the real stout one while the hopes of the Oklahoma injection operators rest on thin reeds.

At least nobody has died, but when you are evacuating a senior housing facility in the night and cancelling school, you know you are playing with fire.

And hey, we aren’t even done with 2016 yet.

Horses, barns and earthquakes

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.

As they sow…

Well, the chickens have come home to roost in Oklahoma.  After spending years obfuscating and denying any role in creating earthquakes in the Sooner State, the oil and gas industry has burned through their political cover and now are being told to cut way back on injecting waste from oil and gas wells into deeper strata.

Had industry taken a more proactive stance some years ago and invested some time and money in determining which wells, under which circumstances, were causing earthquakes, they might not today be facing a downturn in production.  It is quite likely that many of the 411 wells told to cut back were not part of the problem, but figuring that out now is probably very difficult.  Meantime, the fluid already injected over the past several years is likely going to continue to produce earthquakes for some time to come.

Better late than never…

Its been awhile since we visited the homes shaking on the range…

A recent note in Energywire on the likely imminent collapse of one oil and gas company happens to cover a number of actions by regulators in Kansas, Oklahoma and Arkansas that are putting the squeeze on some oil and gas operators in the area.  The cause? Regulators have finally started approaching injection wells with caution.

What is going on, according to the story, is

“…a widespread effort in Oklahoma, Kansas and Arkansas to decrease tremors. Methods include shutting down wastewater injection wells, making the wells more shallow or decreasing the amount of water in each. Operators in Oklahoma made 137 wells shallower since July and decreased the volume in 61 others.

“Arkansas shut down four wells believed to be causing quakes while Kansas halved the amount of wastewater that companies can inject for 72 wells….”

This has hit SandRidge Energy particularly hard as this is their home area; between the reduction in capacity for their disposal wells and the current drop in oil prices, the company faces bankruptcy.

There is nothing like serious financial consequences to get industry’s attention, and the potential failure of a company has got to get the attention of industry leaders. Hopefully the response is to approach the whole injection well process with greater caution; this would be best for all involved.  Most injection wells seem to have little capacity for creating earthquakes, but some clearly do cause them. Allowing for the possibility that a well could cause trouble in planning for the well and budgeting for it  will make it far less likely that troublesome wells will continue to be operated. While this isn’t as strong a message as being directly saddled with liability, it is a good step forward.

Its not like the oil and gas industry never deals with uncertainty.  They have loads of experience in evaluating the prospect of failure in their exploration and production activities; extending this to include issues with seismicity in injection wells should be a no-brainer.

Wait for it….

OK, another day, another mysterious earthquake in the mid-continent.  This time we are talking a M 4.2 in southern Michigan. We have the anti-fracking crowd immediately inferring that fracking caused it; we have a media report that the USGS said it isn’t from fracking (it isn’t clear where that statement originated).

So first some simple stuff.  The nearest seismometer was 75 km away, and only 13 phases have been used to locate the event so far.  That means that the depth based on travel times is nearly worthless (it is reported as 6 +/- 7 km deep, meaning it is in the upper crust).  The USGS moment tensor solution puts it at 8 km, but no uncertainty is included, so it isn’t clear that the solution is constraining the depth very well; Bob Herrman’s moment tensor solution places the earthquake at 5 km down and seems to indicate it is unlikely to be much shallower than 4 km.  Both solutions indicate it is a strike-slip earthquake.

What you want to know is, are there deep injection wells operating in the area? Are they high volume?  Are they new, or recently increased their disposal rate? (Be careful of early pronouncements; many online databases are not up to date).  GG has seen hints there might be such wells.

While this is a suspicious earthquake, it isn’t that far from the Wabash Valley Seismic Zone, a set of faults in southern Indiana and Illinois that have produced large prehistoric earthquakes. But it isn’t that close, either…

So it shall be interesting to see what the story is…

Finger pointing frustrations

Well, the New York Times finally decided to dial in to the ongoing seismic mess in Oklahoma. And while the coverage highlights the potential conflicts of interest and ability of the oil and gas industry in that state to dampen if not entirely prevent criticism of its operations, it doesn’t exactly shed a lot of light on the problems of saying why there are these earthquakes and it doesn’t help folks to understand how these earthquakes might be connected to the wells in question.  Rather than get into the mud and argue the details in Oklahoma (you can read the 2014 Science paper if you want to see how that is done), consider a much simpler system.

For the past 24 years, the Bureau of Reclamation in southwest Colorado has been pumping saline water into a deep aquifer (the goal is to reduce the salinity of Colorado River water reaching Mexico). Unlike most (if not all) of the injection wells associated with oil and gas work, the seismicity of this region was monitored prior to the beginning of injection and has continued to be monitored ever since.

Not surprisingly, small earthquakes started showing up immediately when injection started, and more or less the region influenced by injection has expanded over time (see plot below from Block et al., Seism. Res. Lett., 2014)

Expansion of seismicity from the Paradox Valley injection well over time. (Block et al., Seism. Res. Lett., 2014).

Expansion of seismicity from the Paradox Valley injection well over time. (Block et al., Seism. Res. Lett., 2014).

What is clear from this work is that the effects of the injected fluid are far from simple.  In particular, the generation of seismicity north of the valley without much in the way of intervening events shows just how complex these systems can get.  Drop another 10,000 wells on top of this and see how easy it is to figure out which well is responsible for which earthquake.

Now the New York Times’s explanation for this was, um, a bit opaque: “The mechanics of wastewater-induced earthquakes are straightforward: Soaked with enough fluid, a layer of rock expands and gets heavier. Earthquakes can occur when the pressure from the fluid reaches a fault, either through direct contact with the soaked rock or indirectly, from the expanding rock.” Most of this is somewhere between wrong and misleading.

There are two ways to get earthquakes from messing with fluids: changing the stress field in the earth and changing the pore pressure.  In the first, the weight of a mass of water will increase the vertical normal stress–basically increase the weight on deeper layers.  With the extra weight, these layers will want to thin vertically and expand horizontally (try squishing a ball of Silly Putty more from the top and bottom than the sides and you will get the same result).  If the stress field is extensional, you can generate earthquakes this way.  Some earthquakes induced by filling large reservoirs (e.g., Lake Mead) are caused in this manner.

More common, and probably most relevant in Oklahoma, is the change in pore pressure.  If you were to slice open a rock at depth and push on it to keep it from deforming, the force you would have to use would be fighting two aspects of the rock: how much the mineral material in the rock was pushing out, and how much any fluid in the pores in the rock was pushing out.  This second parameter, the pore pressure, is the likely culprit here.  Injecting fluid will change the pore pressure in the surrounding rocks, and just as atmospheric pressures change without moving the entire atmosphere, so can adding fluid in one area affect the pressure elsewhere without the need for the newly added fluid to travel all the way to some area that has a pressure change. If the pore pressure increases, the normal stress on the mineral part of the rock lowers.  But any shear stresses acting to try to make the rocks slide across a fault are unaffected (water cannot support a shear stress), so the lower normal stress on the rock combined with the continuing shear stress means that the rock will more easily fail on any given fault line. It is a little like hydroplaning when driving a car in a rainstorm; the water is absorbing some of your weight, which reduces the frictional forces that allow you to change direction or slow down. Slipping is a lot easier.

So one big challenge is to pin the tail on the right donkey (something that 2014 paper sought to do).  Ideally we could anticipate when this might happen, but it seems we have thousands of injection wells running in this country that seem to have no impact at all (well, at least not yet). So while it seems nearly certain that some injection wells are causing significant earthquakes, and we may be gaining the ability more and more to figure out which wells are most likely the culprit, we are still quite a ways from knowing ahead of time if a well will cause earthquakes.  In the interim, it would be best if regulators and injection companies kept the possibility of having to shut down a well in every well’s operational plan.