The conductivity of the Marcellus Shale and its overlying units does not currently allow significant
methane migration from depths being considered for natural gas extraction to the surface. If that were the case,the quantity of natural gas stored throughout the Marcellus Shale would have been greatly diminished by now. We might assume, therefore, that the conductivity provided by existing fracture networks connecting the Marcellus to much shallower units is very low. Based on this reasoning, it appears unlikely, though not theoretically impossible, that gas and fracturefluid could migrate to potential sources of drinking water in this way.