Injecting Some Sense Into Fracking Regulation

The July issue of Scientific American carried the best summary of the fracking-earthquake controversy I have seen so far.  "Drilling For Earthquakes" by Anna Kuchment reviews the fracking (hydraulic fracturing), the associated water injection, the earthquakes, the science, and government reactions to the problem.  In particular, the article shows the very different approaches the states of Texas and Oklahoma have taken to the problem.  And I regret to say it doesn't make my native state of Texas look good by comparison.  But first, the basics.

As I wrote in this space in 2013, water-injection wells to dispose of the brackish water that comes up sometimes along with oil and gas are nothing new.  But the combination of fracking to extract fossil fuels from previously inaccessible formations, horizontal drilling to gain wider access to those formations, and the boom of widespread deployment of these techniques that has gone on in the last six or eight years, have led to a huge increase in the volume of water injected back deep underground.  During 2014, in Texas a gallon of water was injected back into the ground for every 100 or so cubic feet of shale gas extracted.  That may not sound like much, but Texas produced about 4 trillion (4,000,000,000,000) cubic feet of shale gas that year.  Leave off two zeroes and that's how many gallons of water were injected back into the ground.  And that ratio probably holds true more or less for the rest of the country as well.

Wastewater injection from fracking doesn't always cause earthquakes.  North Dakota has had a lot of fracking and wastewater injection too, but hardly any earthquakes.  On the other hand, Oklahoma, a place that was hardly famous for earthquakes before 2005, had 581 temblors of magnitude 3.0 or greater in 2014.  Its most severe one recently happened in November 2011, when a 5.6-magnitude quake wrecked more than a dozen houses and injured a couple of people.  Less severe but just as widespread quakes have been happening in North Texas, where the Barnett Shale has been exploited for natural gas in a big way, and injection wells are operating there too.

Because of the huge volumes of wastewater to deal with, oil and gas producers don't have too many options that won't make their operations too expensive to carry out.  Treating the water to extract the salt and other minerals would mean distilling it, a hugely costly process that would turn them all into water-purification plants with an unprofitable sideline of making oil and gas as a byproduct.  So that's not an option.  Trucking it to a place where injecting it wouldn't cause earthquakes would be expensive, even if we knew of a nearby place where injecting it wouldn't cause earthquakes.  And just throwing it out on the ground, which used to be a common practice in the bad old days before 1950 or so, would cause huge amounts of waterway pollution because of the salts, radioactivity, and other nasty stuff that comes up with the water.  So going to the expense of drilling wells typically much deeper than the producing ones and injecting the wastewater downhole at tremendous pressures is the only thing that producers can typically do with it.

The trouble is, rocks are porous—that's the only way you can inject water into them in the first place.  So that high-pressure water starts to move, and seeps toward faults, which are just big cracks between intact blocks of rock.  Some faults are under shear stress.  To envision shear stress, think of holding two old-fashioned chalkboard erasers together face to face and rubbing them back and forth across each other.  It's shear stress you put on them that makes them slide.  If you mash the erasers together perpendicularly, putting them under compressive stress, it's a lot harder to get them to move with shear stress.  So a fault that is under shear stress won't slip and cause an earthquake as long as the compressive stress is great enough.

Then along comes your water injection at high pressure.  It seeps through the pores to the cracks and provides an opposing pressure that can counteract the compressive stress that's keeping the fault from slipping.  We're not talking lubrication here, but large opposing mechanical forces.  I'm sure the technical details involve stress tensors and the whole nine yards of solid mechanics, but the basic picture is simple.  When the fluid pressure exceeds a certain threshold, that fault is going to let go, and you've got an earthquake.  People have even done experiments in the field to figure out exactly how much stress makes the faults slip, and there is a definite threshold, just as theory predicts.

Both from mechanical analyses and statistical studies, as well as abundant seismological data correlating particular regions of earthquake activity with particular injection-well activity, by now it is clear to all but the most biased observers that, generally speaking, the injection-well activity has caused the increase in earthquakes in both Texas and Oklahoma.  The U. S. Geological Survey, which has been issuing long-range earthquake predictions by region for some time now for the convenience of structural engineers, insurance companies, and other interested parties, has had to revise its forecasts for Oklahoma and Texas sharply upward in the last few years.  A contour map of earthquake likelihood for Oklahoma now looks like an archery target with Oklahoma City in the bullseye.  And the scientific literature abounds with studies showing details of the correlation.

Oklahoma has a long tradition of assertive state government, dating back to the 1930s when it passed laws regulating things like the price of ice.  And they have now continued that tradition by shutting down individual wells since 2015 and regulating the volume of wastewater that can be injected.  On the other hand, the Texas agency in charge of oil and gas regulation (for historical reasons, it's called the Texas Railroad Commission) still has not been able to bring itself to admit that any earthquakes have been triggered by water injection associated with fossil-fuel production.  But recently the Commission asserted its right to shut down wells if it wants to.  So far, though, it hasn't wanted to.

To some degree, all this is water under the bridge, or well, as the case may be.  Oil and gas markets are glutted right now, and the consensus is that the big fracking boom is over, at least in Texas and Oklahoma.  But all that injected water is still down there, slowly diffusing, and some geologists estimate that the effects of water injection on earthquakes can last as long as twenty years.  So in that sense, we may be dealing with the aftershocks of the fracking boom for some time.

Sources:  Anna Kuchment's article "Drilling for Earthquakes" appeared in the July 2016 print issue of Scientific American, pp. 46-53.  I also referred to a U. S. Department of Energy table of shale-gas production available at https://www.eia.gov/dnav/ng/ng_prod_shalegas_s1_a.htm.  I blogged on earthquakes and fracking most recently on Dec. 30, 2013.

Fukushima Revisited: Lessons Learned

On Mar. 11, 2011, a huge earthquake and tsunami struck Japan, killing thousands of people outright and flooding large areas of the northeastern coastline of the country.  But perhaps the most significant legacy of the disaster will arise from what happened at the Fukushima nuclear plant, which was situated in the direct path of the tsunami.

As we mentioned in a blog two days after the disaster, no nuclear plant in history had been subjected to an 8.9-magnitude earthquake before.  But all of the six reactors at the plant may have sustained the shock without serious initial damage.  As the earthquake struck, automatic shutdown procedures were followed and after the earthquake, the operating reactors were still under control.  The problems came with the tsunami, which flooded the lowest level of the plant.

At this point, we turn to the conclusions of two special commissions charged with investigating the accident.  Both issued their conclusions just this last July of 2012.  One commission was the first of its kind in the entire sixty-six-year history of Japan’s constitutional government.  After interviewing hundreds of witnesses and conducting over a thousand hours of interviews, the commissions had harsh words to say about Tokyo Electric Power Company (TEPCO), government officials, and the sadly lacking state of emergency preparedness showed by those charged with the safety of nuclear power generally in Japan.

One problem that could have been avoided concerned the location of the emergency generators that kept cooling pumps operating during cooldown.  Turning off a large nuclear reactor is not like just flipping a switch.  They operate by heating large volumes of water, metal, and fuel to many hundreds of degrees, and even if the nuclear reaction is stopped almost instantly by some means such as the insertion of neutron-absorbing control rods, the laws of physics say that all that heat has to go somewhere.  And the usual place it goes is into the cooling fluid that is circulated through the reactor to remove the heat to boilers to generate electricity.

In the case of a shutdown, the heat can be simply dissipated in cooling towers or other rapid means, but first it has to be extracted by the cooling fluid flowing through the reactor.  In an emergency, this fluid has to be pumped even faster than normal, and only mechanical pumps will do the job in the type of reactor used at Fukushima.  With the loss of electric power from outside due to the earthquake and from the plant’s own generators due to the shutdown, the pumps had to be powered by emergency generators that were operating from diesel engines.  The big problem was, all these emergency generators were in the basement—where the floodwaters rose and stopped them cold.

From that point on, the situation just got worse.  With no cooling fluid flowing, the three reactors operating at the time of the earthquake overheated and produced hydrogen from the reaction of water with hot metal inside, and eventually the hydrogen exploded.  This was a chemical, not a nuclear, explosion, but it broke open the plant’s housing enough to release a lot of radioactive trash from the wrecked reactors inside—about a tenth of what was released during the much more serious accident at Chernobyl, Ukraine in 1986.  But enough radioactive material was released at Fukushima to affect the lives of those who lived near the plant for many years.

The fact that the emergency generators were in a vulnerable position where floodwaters could stop them is only one of a number of design flaws that contributed to the magnitude of the disaster.  Higher dikes around the plant site could have conceivably prevented flooding in the first place.  Following a call for increased safety measures at nuclear plants in 2006, TEPCO apparently did little or nothing.  According to the National Diet report, the firm relied on its close connections with Japanese regulators to avoid taking any substantial actions to improve safety.  The reports also faulted government officials for not planning for evacuations of the scale that turned out to be needed.  The Fukushima disaster has also given ammunition for groups agitating for the end of nuclear power altogether, and several countries such as Germany have either slowed or stopped their plans for future nuclear plants.

Admittedly, the earthquake and tsunami that led to the Fukushima disaster were at the outer limits of what any reasonable design would take into account.  But clearly, some fairly simple measures that might have made routine operations a little less convenient would have reduced or eliminated altogether the tragic events that led to the death or injury of numerous plant workers, the release of radiation that contaminated land for miles around the plant, the bad publicity that nuclear power received, and the total loss of billions of dollars’ worth of machinery and equipment.

One hopes that every nuclear engineer, in school and out, will make a special study of Fukushima in order to use the lessons learned from what went wrong there.  With the release of the disaster reports (and, hopefully, their translation into other languages including English), the nuclear industry has been presented with a treasure trove of mostly bad examples of how not to do it.  As engineer and writer Henry Petroski likes to point out, engineers often learn more from failure than from success, and Fukushima has presented us with an abundance of learning opportunities.  In view of concerns over climate change, the availability of fossil fuels, and the promise of conservation technologies such as smart-grid approaches to power distribution, it would be a shame if we back away from a form of energy that could provide non-fossil power for many decades to come.

Sources:  I relied upon the Wikipedia summaries of the commission reports under the headings of “Fukushima Daiichi nuclear disaster” and “National Diet of Japan Fukushima Nuclear Accident Independent Investigation Commission.”