Ask the Experts: Carl Kirby on Marcellus Shale
Carl Kirby, professor of geology.
Posted: February 18, 2010
(Editor's note: "Ask the Experts" will resume weekly publication in the fall. Until then, please enjoy this edition originally posted this past spring.)
LEWISBURG, Pa. — Welcome again to "Ask the Experts," a regular web feature that highlights the expertise of various Bucknellians in a range of topics related to current news events and other timely subjects. || Ask the Experts archive
In this installment, we asked geology Professor Carl Kirby, who has studied acid mine drainage and the effects of its by-product on streams, to talk about Marcellus Shale and the implications of drilling the Pennsylvania formation for gas.
Q: What is Marcellus Shale and its significance to this region of Pennsylvania?
A: About 400 million years ago, fine sediments and organic matter were deposited into an ocean basin that was part of Pennsylvania. That sediment was buried under other sediment and turned into rock - the Marcellus Shale. The organisms were "cooked" by the right amount of heat and pressure to turn them either into oil or natural gas.
Pennsylvania has experienced oil and gas drilling since 1859 when the first commercial U.S. oil well was drilled in Titusville, Pa. Now, there is an expanding "boom" in natural gas extraction from the Marcellus, especially in the Northern Tier and western part of the state.
There's huge potential for the state and individuals to make money by leasing land and receiving production royalties for successful wells. That's one side of the equation. However, as with any extractive industry, there's an environmental cost. The state is trying to balance the environmental costs against the economic benefits.
Many Pennsylvanians know about the physical hazards from the numerous abandoned coal mines and about the mine drainage that has virtually killed hundreds of stream miles, including nearby Shamokin Creek where we take a lot of our students. That mining was done under virtually no environmental regulation, so we have an environmental legacy that no one is legally responsible to clean up. Currently, mines are operated much more responsibly because they're regulated.
Q: How is the gas extracted?
A: Most natural gas extraction from the Marcellus is through horizontal drilling and hydraulic fracturing (hydrofracking). A vertical well is drilled and then the well bore is angled into the nearly horizontal Marcellus at about one mile deep. The hydrofracking water and some other components are blasted at great pressure into the well, breaking the shale up to allow natural gas to reach the surface.
One of the reasons it's a big environmental issue is that hydrofracking requires a lot of water; it takes on the order of a million to 8 million gallons to frack a single well. That water has to come from streams or from municipal supplies. Once the well has been fracked and you've pushed all that water down there under very high pressure, it mixes at depth with a very saline water called an oil field brine.
The brine mixes with the injected water to make frack-water, some of which usually comes back to the surface and can be 10 times saltier than sea water. That causes the need for treatment or some disposal option. One of the disposal options that's considered is re-injecting that water into a deep well. At this point, Pennsylvania is not re-injecting. The water has gone to sewage treatment plants, a bad idea because it kills the bacteria that do the work in sewage treatment plants.
So there's a scramble right now to come up with effective water treatment technologies, including potentially cleaning up the water and then putting it back in the tanker truck and reusing it for fracking again. Some companies also reuse frack-water without treating it first.
Unless there is an on-site treatment facility, you'd have to transport the water, which in Pennsylvania is considered a residual waste, not a hazardous waste, to five to 10 treatment plants across the state that will deal with the hundreds of wells.
Q: Is this a good job opportunity for Pennsylvania, or a good job opportunity for the companies coming in?
A: There will definitely be jobs associated with this. As with a lot of natural resource extraction booms, many of the jobs will go to out-of-state people with expertise. There will be some service jobs in wastewater treatment, transportation, trucking and motels, so there will be ancillary economic benefits. There will also be ancillary economic problems, such as a need for greater road maintenance due to heavy truck traffic.
The scope of the long-term potential and actual environmental concerns are incredibly complex. As an example, the state of New York drafted an 800-page environmental statement. The New York City Department of Environmental Protection wrote its own 80-page report recommending against Marcellus hydrofracking in New York state because of the 9 million people living in the watershed downstream.
There are also land disturbance issues and air quality issues. There's habitat loss since they have to cut through the woods to make temporary pipelines to get to the permanent pipelines because natural gas can only be carried in pipelines. And there's a lot of equipment producing greenhouse gas and using fossil fuels to extract a fossil fuel.
Q: How is your research related to the issue of Marcellus Shale?
A: My students and I are studying the water-rock interaction, the water chemistry of the Marcellus Shale. One emphasis is on modeling how the water chemistry changes from the injection, to mixing with the oil-field brine, to the frack-water, then comparing to measured concentrations of inorganic chemicals in the frack-water.
A second emphasis is on how to monitor potential Marcellus leaks into streams. Groups have proposed monitoring the conductivity of streams to check for leaks. The supposition is that if the conductivity of a stream goes unusually high, that would be a Marcellus leak.
Our modeling suggests if a million gallons (enough to do one hydrofrack) spills into a small stream quickly, you'd probably be able to detect the salty water. However, if the spill occurred into a larger stream or even in a small stream during a flood, it would be very difficult to recognize. Conductivity might go down instead of going up because of dilution. So there are some real concerns about trying to use conductivity.
We want to develop a geochemical "signature" for the Marcellus, kind of like a fingerprint, to distinguish normal surface water from surface water mixed with Marcellus water to determine if we've actually had a problem due to Marcellus Shale drilling.
New editions of "Ask the Experts" will appear on the Bucknell website on most Thursdays during the fall and spring semesters and on occasion throughout the summer. If you have ideas for future questions or are a faculty or staff member who would like to participate, please contact Sam Alcorn.
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