Jan wrote:
The old gas wells went down only a few hundred feet, so leaks did
not threaten the aquifers. The new drilling techinque
("hydrofracking") is far more invasive. It goes down thousands of
feet to the Devonian levels, dredges up radiation, uses carcinogens
in the process, and employs horizontal drilling, which greatly
increases risk of contamination of aquifers....
Up in Pennsylvania, one needs to drill down thousands of feet to get
to the Devonian stratum. Here in Ithaca, you only need to walk to any
exposed bedrock to touch the Devonian stratum. Better to write that
"It goes down thousands of feet to the lower Devonian strata." Or
more specifically "to the Hamilton Group." Or, possibly "through the
Devonian strata."
The further one travels towards Lake Ontario, in general, the older the rock.
Also, rock that is very near the surface isn't going to hold natural
gas very well. NG needs to have a cap. It's nice to have a bed-liner
too. In the case of the Marcellus (guess where this shale can be seen
at the surface), those are the Tully limestone (guess where that
reaches the surface) and the Onondaga limestone (ditto). So, in
general, the further south from Tully, the deeper one has to drill;
if you're north of Tully, just stick out your tongue or light a match.
Tompkins county is likely sitting on a resevoir because the Onondaga
limestone is about 600m down, and the Tully is about 300m down, give
or take 200m depending on whether your on a hill or on the lake. In
Lansing and lakeside Ulysses, because of the salt dome and a fault
and a fold and an ancient river delta from the Adirondacks, it's even
shallower, sometimes exposed. In all parts of Ovid, Tully should be
less than 100m down.
So, yes, in PA, hydrofracking will occur thousands of feet down, but
here shallow wells, for better (less equipment) or for worse (closer
to our wells/schools/homes), will be the norm.
I hope people don't use this little detail for quarrels with the rest
of Quarles' statement. It corrals important points about democracy,
accountability, and other serious concerns. (BTW the limestone came
from corals, partly. Maybe we can make some bad puns and rhymes here.)
This interesting tidbit from the NYS Geological Association meeting
of 1959, held at Cornell:
"In the latter part of the [19th] century, enough gas was supplied by
shallow wells in the Lower Silurian Medina sandstones to provide most
of the village of Seneca Falls for about 20 years." If those
suffragettes kept it local, it couldn't be 100% evil. Still, I vow to
keep my house even colder this winter, for the sake of all those
living south of Marcellus.
-Shawn Reeves
[email protected]
Not necessarily the opinion of EnergyTeachers.org
http://energyteachers.org
501(c)(3), 'nough said
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