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Monday, September 15, 2014

Paper: residual frack water not a threat to groundwater

Researchers from Penn State University and Cornell University, along with a geologist from Royal Dutch Shell, say that water injected during hydraulic fracturing operations remains locked in the shale formation and poses no threat to groundwater supplies.

Their paper - The fate of residual treatment water in gas shale - was published in the September issue of the Journal of Unconventional Oil and Gas Resources.

According to Natural Gas Intel, the researchers found that water that gets driven into the shale in the fracking process stays there:
According to the report's abstract, "more than [5 million gallons] of water containing additives is commonly injected into a typical horizontal well in gas shale to open fractures and allow gas recovery. Less than half of this treatment water is recovered as flowback or later production brine, and in many cases recovery is [less than] 30%"… 
"Some have suggested that this RTW poses a long term and serious risk to shallow aquifers by virtue of being free water that can flow upward along natural pathways, mainly fractures and faults," the researchers said. "These concerns are based on single phase Darcy Law physics, which is not appropriate when gas and water are both present. In addition, the combined volume of the RTW and the initial brine in gas shale is too small to impact near surface aquifers even if it could escape. 
"When capillary and osmotic forces are considered, there are no forces propelling the RTW upward from gas shale along natural pathways. The physics dominating these processes ensure that capillary and osmotic forces both propel the RTW into the matrix of the shale, thus permanently sequestering it." 
The research was funded by the Research Partnership to Secure Energy for America and Penn State’s Appalachian Basin Black Shale Group.  Predictably, critics pounced on the funding sources for the study (as well as for another study I blogged about last week). The answer to all of that is more study and application of the scientific process and peer-review.


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