I guess I wasn't the only one who studied our local geologic strata and concluded there might be some extended cracks between layers.
For me, that was mostly what I got from reading the patron geologist of the Marcellus Shale, but people with more skill, money, and time have taken a closer look, and found signs that fluid does move between the layers:
We present geochemical evidence from northeastern Pennsylvania showing that pathways, unrelated to recent drilling activities, exist in some locations between deep underlying formations and shallow drinking water aquifers. Integration of chemical data (Br, Cl, Na, Ba, Sr, and Li) and isotopic ratios (87Sr/86Sr, 2H/H, 18O/16O, and 228Ra/226Ra) from this and previous studies in 426 shallow groundwater samples and 83 northern Appalachian brine samples suggest that mixing relationships between shallow ground water and a deep formation brine causes groundwater salinization in some locations.
The strong geochemical fingerprint in the salinized (Cl > 20 mg/L) groundwater sampled from the Alluvium, Catskill, and Lock Haven aquifers suggests possible migration of Marcellus brine through naturally occurring pathways. The occurrences of saline water do not correlate with the location of shale-gas wells and are consistent with reported data before rapid shale-gas development in the region; however, the presence of these fluids suggests conductive pathways and specific geostructural and/or hydrodynamic regimes in northeastern Pennsylvania that are at increased risk for contamination of shallow drinking water resources, particularly by fugitive gases, because of natural hydraulic connections to deeper formations. (Emphasis added.)
I'm sure the gas companies and friends will think the italicized part of that is critical - these connections weren't created by drilling. However, the most important part is the bold - these connections already exist. We don't know where they are or how they work, but there is opportunity for migration of fluids and especially gases.
The shale-gas-friendly DotEarth blog has a nicely detailed (if corrected) report that talks with one of the authors of the report and a critic, that same patron geologist of the Marcellus Shale.
Posted by simon at July 11, 2012 5:27 PM in energy , geology