This would only happen however if the rocks were extremely porous, yet if this were the case the natural gasreservoir would have never existed in the first place.
To begin with, the vertical depth separation between drinking water aquifers and reservoir targets for gas production is several thousand feet of impermeable rock.
This is the same gas responsible for recent coal mine accidents, and it can infiltrate the water reservoir if there is too much pumping, which creates a pressure draw down.