Take the time to read this article from yesterday's Times-Tribune. Read it slowly, especially this section:
The geology in Northeast Pennsylvania is also complicated and, in some rural regions, rarely studied, meaning there were few good historical maps for the drillers' reference, said Fred Baldassare, a former stray gas inspector with DEP who now owns Echelon Applied Geoscience Consulting.
"It's a very complex system with deep-seated fractures and deep-seated thrust faults that come to the surface," he said. "These are pathways that are now being understood by industry that maybe at the beginning of the drilling process here they weren't appreciating."
The shallow methane is not necessarily uniform in the layers above the Marcellus. It is present in "a variety of strata - very shallow all the way down through," said Scott Perry, the director of DEP's Bureau of Oil and Gas Management. "There's a lot of shallow methane and there's a lot of pathways for it to get into groundwater because of the geology."
Natural gas shales like the Marcellus slowly release gas over hundreds of millions of years, and the drifting methane gradually penetrates the porous rock layers above them, Dr. Engelder said.
The drift of gas upward from shales is well known and occurs in regions like Texas and Arkansas, where shale-gas drilling began years before operators turned to the Marcellus, Dr. Engelder said.
Asked why gas drillers did not anticipate the pockets of shallow gas in Northeast Pennsylvania, he said, "The only explanation of course is that the operator was a little bit careless."
Simply put, if the gas can migrate through the "porous" layers above the Marcellus, and there is a complex system of unmapped fractures and faults in the bedrock, and thousands of new wells will be drilled into the Marcellus Shale...who is to say nothing else can migrate?
The operator was "a little bit careless"? How about clueless?
The aftermath of this article should be fun to watch.
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