Possible contamination pathways from fracking
Previous research on hydraulic fracturing has indicated possible contamination of water wells by methane. A new research article attempts to model potential contamination pathways to aquifers from Marcellus shale gas beds.
As unconventional natural gas sources are increasingly exploited, recent research has pointed to possible threats to groundwater from hydraulic fracturing, or “fracking”. The Marcellus shale underlying New York, Pennsylvania, Ohio and West Virginia is the largest known deposit of shale and the most studied. Building on previous research measuring water impacts from shale gas development, Myers, in a recent paper, assessed the possible pathways of contamination through shale beds to aquifers using MODFLOW, a 3D groundwater modeling software. The findings were published in Ground Water earlier this year.
Myers attempts to characterize risk and mechanisms of transport of gases between shale beds and aquifers. The MODFLOW model assesses several possibilities of transport from shale, using estimates from southern New York. The model estimates shale 30 meters (98.4 feet) thick and 1500 meters (4,921 feet) underground, covered by sandstone up to the surface. The model begins with a baseline and proceeds to layer on scenarios meant to estimate the effects of fracking on a possible change in the subsurface.
Results indicated hydraulic fracturing could change the flow of gas underground, and that the transport time from the shale to aquifers could decrease from thousands of years to as few as 10 years. The model also indicates increased pressure underground near the wellhead for up to 300 days after fracking. This could be a cause for mediation or concern.
The importance of this paper and further research on contamination pathways is clear. Although the model was simplistic, it shows fracking can be modeled via MODFLOW, and this study is the first to attempt to model the mechanisms of possible impacts on groundwater.
The author recommends geological mapping of the subsurface both pre- and post-fracking, especially around faults, so distance from faults can be maintained. The author also seconds other researchers in recommending aquifer and water well monitoring in areas with significant shale gas development.