The problem is not what you've been told.
Utilizing a new method of geochemical forensics to trace how methane migrates under the earth, a team of researchers uncovered the likely source of most natural gas contamination in drinking-water wells associated with hydraulic fracturing--and it is not the source many people may have feared. What is more, the problem may be fixable: improved construction standards for cement well linings and casings at hydraulic fracturing sites.
The study identified eight clusters of contaminated drinking-water wells in Pennsylvania and Texas. Most important among the findings is that neither horizontal drilling nor hydraulic fracturing of shale deposits seems to have caused any of the natural gas contamination.
"There is no question that, in many instances, elevated levels of natural gas are naturally occurring but, in a subset of cases, there is also clear evidence that there were human causes for the contamination. However, our data suggests that where contamination occurs, it was caused by poor casing and cementing in the wells," says study leader Thomas Darrah, assistant professor of earth sciences at Ohio State University, Columbus, who was aided by researchers from Duke University, Durham, N.C.; Stanford (Calif.) University; Dart mouth College, Hanover, N.H.; and the University of Rochester (N.Y.).
In hydraulic fracturing, water is pumped underground to break up shale at a depth far below the water table. The long vertical pipes that carry the resulting gas upward are encircled in cement to keep the natural gas from leaking out along the well. The study suggests that natural gas that has leaked into aquifers is the result of failures in the cement used in the well.
"Many of the leaks probably occur when natural gas travels up the outside of the borehole, potentially even thousands of feet, and is released directly into drinking-water aquifers," explains Robert Poreda, professor of geochemistry at the University of Rochester.
Adds Avner Vengosh, professor of geochemistry and water quality at Duke, 'These results appear to rule out the migration of methane up into drinking water aquifers from depth because of horizontal drilling or hydraulic fracturing, as some people feared."
Concludes Darrah, "This is relatively good news because it means that most of the issues we have identified can potentially be avoided by future improvements in well integrity."
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|Title Annotation:||Hydraulic Fracturing|
|Publication:||USA Today (Magazine)|
|Date:||Dec 1, 2014|
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