Shawn raises an interesting point here. At some depth, the shale layer will
lose the gas it might otherwise contain. By the time the Marcellus surfaces
in Marcellus, any gas is long gone. Just how far south do you have to go
before there are economically viable amounts of gas to extract? a geologist
friend of mine thinks Tompkins County is unlikely to worth exploiting. I'd
be interested in Shawn's take on that.
Joel
At 06:36 PM 9/2/09 -0400, you wrote:
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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_______________________________________________
For more information about sustainability in the Tompkins County area, please
visit: http://www.sustainabletompkins.org/
RSS, archives, subscription & listserv information for:
[email protected]
http://lists.mutualaid.org/mailman/listinfo/sustainabletompkins
Questions about the list? ask [email protected]
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