The Rising Influence of Rising Affluence

[OakesCS]

nah, the drilling isn't a problem. Firstly, the concerns of folks overlying the Marcellus are that additives in the frack fluids are entering their drinking water aquifers. Methane is just for sensationalist demonstrations (as in Gasland). There are many additives and they vary in identity and usage; however, they may include biocides, surfactants, pH buffers, viscosity modifiers, etc.
http://geology.com/energy/hydraulic-fracturing-fluids/

I suspect the biggest concern involves biocides. You could drink a lot of water saturated with methane and you'd probably die of water intoxication before suffering any ill effects from the methane.

There are 2 scenarios where human activities could conceivably cause or allow methane or fracturing fluids to enter an aquifer above a gas reservoir: 1. a bad or compromised cement job which allows stimulation fluids or produced fluids to migrate up the well between the outside of the cement and the wellbore; and 2. the fracking operation penetrates a cap rock or opens pre-existing fractures through a cap rock and thus provides a conduit for stimulation or produced fluids (natural gas, oil, or brine) from the reservoir to migrate upward to an aquifer.

The 1st scenario is acknowledged by the PNAS paper's authors as being a possible culprit for the methane in their samples. Of course, that methane might also be from other reservoirs above the Marcellus and might have nothing to with drilling. In any case, bad cement jobs do happen so it should not be automatically discounted as a possible contributor to groundwater contamination.

The 2nd scenario is also possible - nobody has definitively shown that it is not be possible. However, The fracturing fluids do not flow upward unless they are either more buoyant (less dense) than the overlying fluids or there is a pressure gradient which forces the fluids upwards even if they are more dense. Even if either of those occurred, there is usually flow in the overlying aquifers and several thousand feet of rock over the reservoirs. That means any leakage will be diluted and swept 'downstream'. So anybody who claims that their well water is contaminated by a nearby gas well is probably almost certainly wrong unless the gas well has a bad cement job or there are some really long and open fractures that will almost certainly be very obvious. Since the latter are not observed, then the choices are either folks should look 'upstream', or look at the cement jobs, or look for a different source for the methane.

I believe that Halliburton and Schlumberger have both released the identities of the chemicals used in their fracturing fluids. If you google: fracturing fluid chemicals site:halliburton.com or slb.com you'll come up with much more specific information.