A report published Monday concludes that, in areas of the country where natural gas drilling is common, recent cases of natural gas migration into drinking water sources likely are not the direct result of horizontal drilling itself nor of the hydraulic fracturing process, but rather can be traced to instances of defective well construction.
Researchers from five universities sought to identify whether elevated gas levels were a result of human activity and what mechanisms caused the elevated levels. The report examines data from “eight discrete clusters of fugitive gas contamination”—seven from the Marcellus Shale area and one from the Barnett Shale area. The researchers, in what they believed to be a first-of-its-kind methodology, used noble gas isotope data to trace the geologic strata that was the source of any natural gas present in the drinking water.
The authors concluded that four clusters of fugitive gas contamination were caused by failures of annulus cement in the well itself, which allowed gas from intermediate strata to leak into water supplies. Three clusters were caused by faulty production casings, which allowed target production gasses to migrate into the groundwater. And one cluster of target production gas migration was caused by an underground gas well failure. The data “do not suggest that horizontal drilling or hydraulic fracturing has provided a conduit to connect deep Marcellus or Barnett Formations directly to surface aquifers.”
The report adds to the growing support that horizontal drilling and hydraulic fracturing are not abnormally dangerous when conducted properly. In an e-mail to the Dallas Morning News, lead author Thomas Darrah of Ohio State University said “[t]his 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.”
Read "Noble gases identify the mechanisms of fugitive gas contamination in drinking-water wells overlying the Marcellus and Barnett Shales" article.
This post was written by Barclay Nicholson (barclay.nicholson@nortonrosefulbright.com or 713 651 3662) and Michael Gaetani (michael.gaetani@nortonrosefulbright.com or 724 416 0400) from Norton Rose Fulbright's Energy Practice Group.
