Scientists rebut study linking hydraulic fracturing and groundwater contamination

Last year, hydrologic geologist Tom Myers’ conclusion that hydraulic fracturing of deep shale gas wells can be expected to impact shallow groundwater aquifers in less than ten years received much publicity, especially among environmental groups who had funded the work. Myers' findings appeared in an article entitled, “Potential Contaminant Pathways from Hydraulically Fractured Shale to Aquifers,” which appeared in the November/December 2012 issue of Groundwater, the journal of the National Groundwater Association. In response, a group of scientists from the Pennsylvania Geological Survey and the Pennsylvania Council of Professional Geologists have published a rebuttal of Myers’ work.

These scientists found many deficiencies with Myers’ modeling simulation, including a lack of objectivity and a” lack of understanding how to develop a credible hydrogeological conceptual site model.” They questioned Myers’ conceptual site model as not comprising the following (1) an accurate representation of the study area’s geology; (2) how hydraulic fracturing can be expected to modify the shale reservoir’s natural fracture characteristics; and (3) proper insight into the hydrodynamic and pore conditions of the rocks through which the water and hydrocarbons flow. As a result of their findings, the scientists have determined that Myers’ is fatally flawed with misinformation. Some examples include:

• The geology overlying the Marcellus Shale formation is an alternating series of sandstones, siltstones, shales, and carbonate rocks that vary in thickness, extent, and rock physical properties depending on location. Myers incorrectly based his model on “predominantly sandstone” overlying the formation. 
• Fracture orientations in rock vary with both depth and lithography and cannot be presumed to be vertical throughout an entire sequence of sedimentary rock. Unsupported by empirical data, Myers assumed a continuous 19.7 ft. wide, vertical, high-permeability fault extending from the Marcellus Shale formation at depth to ground surface.
• Myers’ assumption of continuous upward flow from the Marcellus Shale to shallow groundwater aquifers would require that the sedimentary sequence between the shale and the aquifers be completely saturated with water. Extensive oil and gas drilling and production as well as geological studies have demonstrated that the shale is highly under-saturated with water. “There is no evidence to suggest that upward fluid migration has been continually occurring in the Appalachian basin. In fact, were this an active process throughout geologic time, the fresh groundwater aquifers currently sourcing more than one million private water supplies in Pennsylvania alone would not be fresh – instead, they would be unpotable.”

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This article was prepared by Barclay Nicholson (bnicholson@fulbright.com or 713 651 3662) from Fulbright's Energy Practice Group.