Stanford scientists have found the best
evidence so far that injections of wastewater from hydraulic fracturing
(fracking) oil and gas wells definitely cause earthquakes. The next question is, how will the
Texas Railroad Commission and the oil and gas industry respond? But first, the scientists' study.
As readers of this blog may know, fracking
involves the injection of special mixtures of water and proprietary stuff at
extremely high pressure into specially drilled wells that penetrate oil- and
gas-bearing formations which normally would not produce enough to be worth
drilling into. The producing wells
are not the problem. The problem
is that a byproduct of the process is a huge amount of wastewater contaminated
with salt, chemicals, and sometimes even radioactive stuff, and these days you
don't just dump it out on the ground or into a nearby stream. The drillers gather it up with tank
trucks and ship it to disposal wells, where it is squirted several kilometers
deep into rock formations under tremendous pressure.
It's these disposal wells that seem to be
associated with spates of earthquakes in north Texas and Oklahoma, which up to
2000 or so were some of the most earthquake-free areas in the U. S. Fortunately, most of the earthquakes
have been small—around 3 on the "moment magnitude" scale, which
replaced the old Richter scale in the 1970s. But a 4.8-magnitude quake on May 17, 2012 in the East Texas
town of Timpson (about halfway between Lufkin and Longview) knocked down a
brick wall, and turned out to be the largest such quake ever recorded in that
area in recent times.
Stanford geologist William Ellsworth,
working with an international team of geophysicists, remote sensing experts,
and others, decided to build a model of the subsurface rocks to see if they
could reproduce the conditions that may have led to the earthquake. Fortunately, that part of Texas is
well-understood geologically, and Ellsworth's team obtained data on how much
wastewater was injected into two pairs of wells, each at a different
depth. They also found and
enhanced satellite-radar data that can measure movement at the earth's surface
as slight as 1 millimeter per year.
They put all this data into a "poroelastic layered Earth
model," meaning they accounted for porosity and elasticity—how holey and
how flexible the rocks are. They
also knew about existing faults, and ran their model to predict both how much
the surface might bulge after getting some 800,000 cubic meters of wastewater
injected into it per year for several years. Then they compared their model's predicted bulge to the
measured bulge, which was several centimeters, and got pretty good agreement between
their model and the actual satellite data.
That told them that another number their
model produced—the increase in pore pressure—was also probably right. When pore pressure increases by about
10 times atmospheric pressure (1 megapascal or more), this has been shown to
cause earthquakes. The mechanics
are complicated, and I'm not a mechanical engineer. Basically, the reason fault lines under pressure don't slip
is that there is a lot of force squeezing the two sides together, and the
resulting friction keeps things stationary. But when you have increased pore pressure on the order of 1
megapascal, that somehow decreases the squeezing force and the thing starts to
slip. And slip it did, causing
Timpson's quake and others.
Although most of the bulging occurred around
the eastern pair of wells, the western wells were where the earthquake
happened. Ellsworth's team could
explain this by citing differences in the porosity and elasticity of the rocks
around each set of wells.
So the scientists have made a model of the
rocks under Timpson, injected their rock model with wastewater, and observed
both a surface bulge that matches what satellites actually measured, and noted
pore-pressure changes of a size that is known to cause earthquakes
elsewhere. And in fact, an
earthquake happened. Looks pretty
conclusive to me. But I'm not a
Texas Railroad Commissioner.
What have railroads got to do with oil and
gas production? It's a long story,
but basically, the Texas Railroad Commission (TRC), which originally did
regulate railroads, backed into the business of granting permits for oil and
gas production in the 1930s, and as time went on nobody has had the temerity to
change its name. It apparently did
some useful work in the 1930s by putting the brakes on absurd overproduction
and keeping oil prices from vanishing.
Nowadays, its regulatory duties are different, and involve environmental
concerns as well as the usual support and encouragement of the industry it is
charged with regulating.
In reports describing the Stanford study,
attempts by reporters to get a reaction out of the TRC were initially
unsuccessful. The Commission's
mission statement has three bullets, saying it serves Texas through (1)
"our stewardship of natural resources and the environment" (2) "our concern for personal and community
safety" and (3) "our support of enhanced development and economic
vitality for the benefit of Texans."
Judging by the Commission's past reluctance to admit any causal link
between fracking and earthquakes, their mission statement's bottom line, about
enhancing development and economic vitality, appears to be taking precedence
over the other two items, just as a company's bottom line tends to take
precedence over other concerns.
Ellsworth and company have confirmed what
many other geologists, as well as numbers of ordinary citizens, have been
suspecting for a long time. Most,
if not all, of the increased earthquake activity in regions near wastewater
injection wells can probably be attributed to those wells.
By and large, Texans are reasonable
people. Fracking has been an
economic blessing to many parts of the state, and it's unlikely that anything
like the blanket fracking bans in New York and Maryland could happen here. But now that there is reasonably good
evidence of the connection between wastewater wells and earthquakes, it would
only be reasonable for people who have lost property or been injured in such
events to ask for compensation from the owners of the wells. Of course, any time lawyers get
involved, reason may fly out the window, but I think we can work these issues
out without either continuing to deny that there's any association at all, or
saying that fracking is an invention of the Devil and must be abolished from
the planet. Let's hope so, anyway.
Sources: I referred to a report published online
by the Dallas Observer on Sept. 23,
2016 at http://www.dallasobserver.com/news/new-scientific-study-cites-direct-evidence-that-texas-quakes-are-manmade-8736998,
one in the Dallas Morning News at http://www.dallasnews.com/news/state/headlines/20160923-texas-quakes-caused-by-injection-wells-scientists-determine.ece,
and the paper by M. Shirzaei, W. L. Ellsworth, K. F. Tiampo, P. J. González,
and M. Manga, "Surface uplift and time-dependent seismic hazard due to
fluid injection in eastern Texas," Science,
vol. 353, Issue 6306, pp. 1416-1419, as well as the
Texas Railroad Commission website www.rrc.state.tx.us.
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