On oil drilling and seismic activity

13 Sep 2006

Got questions about the environment? Ask Umbra.

Dear Umbra,

How is drilling for oil affecting the stabilization of our planet? I wonder how much all the drilling is disturbing the earth's crust. Could this be part of the problem causing tsunamis, earthquakes, and tidal waves?

Susan Milliner
Cedar Park, Texas

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Dearest Susan,

Oil and gas drilling can do all kinds of nasty things to the earth -- including contaminating groundwater, leaving giant waste pits behind (not to mention those big holes), employing toxic chemicals, necessitating road-building, marring views, and polluting the air -- but destabilizing the entire planet ain't one of 'em.

They make messes, but not earthquakes.

Photo: iStockphoto

Given that there are so many dang oil and gas wells (some 700,000 in the U.S. alone), your concern is understandable. But even with so many holes, the planet isn't in danger of large-scale geologic rockin' and rollin'. You see, the deepest among the drill holes plunge down about six miles, and the earth's crust averages some 20 to 40 miles deep on the continents. And while extracting oil -- an estimated 1 trillion barrels worldwide so far -- can have some geological consequences, they aren't major. Frankly, pollution from drilling and burning oil and gas is much more of a danger.

Let's revisit Earth Science class, and remember that earthquakes are caused by the shifting of various tectonic plates that nudge each other and catch on one another and generally play a hefty game of bumper cars, though with billions of tons of rock. Fun! The crashing about causes some 500,000 detectable earthquakes in the world each year, though only about a fifth of them can be felt by humans, and only about 100 of them cause damage.

While the plate drama and other natural geological goings-on are what cause practically all quakes, according to the U.S. Geological Survey, it is possible for humans to cause earthquakes as well. Don't you feel powerful? This is oil-related, though not directly a result of drilling. USGS says the cause of the few earthquakes triggered by humans "was injection of fluids into deep wells for waste disposal and secondary recovery of oil, and the use of reservoirs for water supplies." They go on to reassure us that most of these quakes were minor, and that other human activities, even nuclear detonations, have not been linked to earthquake activity. Whew.

Since tsunamis are essentially big water surges caused by earthquakes, and since drilling itself doesn't cause quakes, tsunamis are one more destructive phenomenon that is beyond drilling's purview. Tidal waves, as it happens, are caused by the many and varied gravitational interactions between the moon, the sun, and the earth, a force oil companies haven't been able to mess with -- yet.

But here's a wacky new angle to worry about, if you're so inclined: While drilling for oil doesn't cause earthquakes, burning oil -- and heating up the planet in the process -- just might. As the Canadian Press reported this summer, "A number of geologists say glacial melting due to climate change will unleash pent-up pressures in the Earth's crust, causing extreme geological events such as earthquakes, tsunamis, and volcanic eruptions." So, we seem to be on shaky ground after all.

Solidly,
Umbra

Yours is to wonder why, hers is to answer (or try). Please send Umbra any nagging question pertaining to the environment -- but first check out her FAQs!

The claims made in this column may not reflect the views of this magazine. Neither the magazine nor the author guarantees that any advice contained in this column is wise or safe. Please use this column at your own risk.

Umbra Fisk is Grist Research Associate II, Hardcover and Periodicals Unit, floors 2B-4B.

Comments: (2 comments)

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Seismic oil mapping has nothing to do with this?

One of the techniques used by the oil industry to find these hidden reserves of "black gold" is to use high-energy vibrations and powerful concussive blasts -- by setting up an array of microphones and using these to feed a huge computational source, the hidden geological formations can be deduced. It's surprising to me that there was no mention of these energetic exploratory techniques and the triggering of earthquakes. It's not beyond my imagination to envision a mapping effort like this happening far out at see, which dislodges some underwater shelf (which may have been storing up the tension required for a good earthquake for quite a while), which displaces a few million tons of water, which in turn creates a devastating tsunami.

Of course, this may just be the product of my fluid logic and a desire to crucify those greedy, repressive jerks at the oil companies.

by rrrandy at 1:37 PM on 13 Sep 2006

seismic shaking and permeability

www.earthchangestv.com

Water and Oil Displacement and Earthquakes

New research has established a new technique for extracting oil. Studies show that by shaking the ground it causes what is referred to as "permeability". 'Permeability' is defined as: "the capability of a porous rock or sediment to permit the flow of fluids through its pore spaces."

Earth Changes Media has discovered a credible research project initiated for peer-review which was recently released and is now available for public viewing. This release comes from the University of California at Santa Cruz 'earth sciences' department. It is authored by Professor Emily Brodsky, assistant professor.

"The enhanced permeability caused by seismic shaking could potentially be harnessed to help extract oil from natural reservoirs. Permeability governs how fluid flows through rocks, whether it's water or oil, so this has practical implications for oil extraction," Brodsky said.

Brodsky is co-author of a paper describing the new findings is now published in the scientific journal 'Nature'. The first author is Jean Elkhoury, a graduate student who worked with Brodsky at UCLA, and the other co-author is Duncan Agnew of UC San Diego. The study was based on two decades of data from the Piñon Flat Observatory in southern California, where researchers from UCSD's Scripps Institution of Oceanography maintain an extensive geophysical observatory.

First for our science colleagues: In essence, net extraction of oil and water reduces slightly the average density of the upper crust, causing an isostatic imbalance. The ductile lower crust deforms in response to this imbalance, thus increasing the load on the seismogenic layer, which fails seismically to thicken the crust so as to restore static equilibrium locally. Accordingly, earthquakes near the base of the upper crust may be an expected outcome of major oil production from growing anticlines, irrespective of the depths of the producing formations.

Now in plan English: When thrusting or extracting oil or water, it causes an imbalance in the Earth's crust or mantle. A natural consequence is for the Earth to find its equilibrium (balance) causing a shift in plates or crustal displacement. This is best known to you and me as an "earthquake".

raven feet on the ground, see from your crown, live from your heart

by haqiqu at 7:48 AM on 14 Sep 2006

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Shaky Reasoning

On oil drilling and seismic activity