Discussions about the potential for environmental contamination associated with energy exploration and production inevitably lead to agreement on the value of unbiased technical evaluation to expose the truth and provide answers uninfluenced by emotion. Two recent studies by academia indicate that hydraulic fracturing to liberate shale gas does not cause contamination of drinking water aquifers but faulty well construction can enable methane to migrate posing risks.
On September 10, 2014, a team of scientists from Pennsylvania State University, Cornell University and Shell International Exploration and Production, Inc. released a study concluding that contamination of groundwater aquifers from water injected during hydraulic fracturing is unlikely because the shale strata acts like a sponge to retain the water through capillary forces in a process referred to as “imbibition.” The researchers conducted the study to evaluate the potential that injected water which remains in place (referred to as residual treatment water or “RTW”) after the flowback water returns to the surface (which is often less than 30% of the injected water) may eventually migrate upward through faults and fractures.
Penn State’s Terry Engelder, Professor of Geosciences, explained:
Imbibition into gas shale is made possible by the high capillary suction that a fine-grained, water-wet shale matrix can exert on water. As water is wicked into gas shale, the natural gas in the shale is pushed out. The capillary forces that suck the RTW into the gas shale keep it there. The practical implication is that hydrofracture fluids will be locked into the same ‘permeability jail’ that sequestered overpressured gas for over 200 million years. If one wants to dispose of fracking waters, one could probably not choose a safer way to do so than to inject them into a gas shale.
“Residual hydraulic fracturing water not a risk to groundwater”, Patricia Craig, Penn State News (September 10, 2014).
In a separate study released on September 15, 2014, researchers from Ohio State University, Duke University and the University of Rochester concluded that faulty well construction accounts for methane migrating into groundwater. The researchers used noble gas and hydrocarbon tracers to identify the sources of methane in studies of the Marcellus Shale in Pennsylvania and the Barnett Shale in Texas. The authors identified seven discrete clusters of natural gas contamination in the Marcellus and one in the Barnett Shale where leakage occurred from failures of annulus cement, faulty production casings and underground gas well failure, leading them to conclude “Noble gas data appear to rule out gas contamination by upward migration from depth through overlying geological strata triggered by horizontal drilling or hydraulic fracturing.”
The studies support what many consultants to the energy community have long recognized. Hydraulic fracturing is an appropriate method to extract gas from shale but care must be exercised to assure that operations are planned and conducted in accordance with recognized industry standards. Further, the problem is exacerbated when domestic water wells are constructed improperly which has been a problem in Pennsylvania. The following is from the Pennsylvania Department of Conservation and Natural Resources website “Frequently Asked Questions bout the Water-Well Program:”
Does using a licensed driller insure my well will be properly constructed? Unfortunately it does not. Drillers are NOT required to demonstrate knowledge of proper drilling or well construction practices in order to become licensed. Pennsylvania has developed construction standards for public water-supply wells, but not for private water wells. There are no statewide construction standards for domestic supply wells. Visit the Department of Environmental Protection (DEP) web page on private wells for more information. Also, check with your township or county government for applicable local ordinances.
Industry standards will continue to evolve to assure that methane is safely captured and delivered to supply our energy needs without adverse impact to the environment. Many hope that Pennsylvania and other states lacking adequate regulations will take steps to assure that domestic water wells are properly constructed to assure that contaminants do not expose risk to users.