The National Energy Technology Laboratory (Pittsburgh, PA) released a comprehensive report on September 15, 2014, titled “An Evaluation of Fracture Growth and Gas/Fluid Migration as Horizontal Marcellus Shale Gas Wells are Hydraulically Fractured (HF) in Greene County, Pennsylvania.”1 This study was designed to look for evidence of groundwater or aquifer contamination produced by hydraulic fracturing of six wells in the Marcellus Shale. Baseline studies before and after fracturing using a variety of techniques showed no communication of the fracking zone with the overlying aquifer. These are separated by several horizontal formations totaling about 5000 ft.
The study employed several tracer methods to look for adverse effects of hydraulic fracturing and found none. Methods included isotopic ratio of hydrogen carbon and strontium plus fluorocarbon tracers. “Current findings are: 1) no evidence of gas migration from the Marcellus Shale; and 2) no evidence of brine migration from the Marcellus Shale.”2
However, I was very impressed with the graphics of the well drilling and hydraulic fracturing process as shown in Figure 8. The microsonic transducers clearly show the locations of fracturing of the shale during the HF process.
Chemists will also find detailed methods for isotopic ratio analysis and sampling.
Kevin Begos of the Associated Press in Pittsburgh, PA quickly pointed out that other adverse events seem to correlate with hydraulic fracturing, but faulty well construction, particularly cementing, was generally blamed.3 Deep Water Horizon is the most conspicuous case in point. Halliburton’s cementing job did not work, and the Gulf, BP, and the USA have each paid dearly.
Is this the definitive study? Probably not, since the relevant geology of shale oil and gas around the U.S.A. differs significantly. However, the report also shows that the technology specialists tried to push the envelope of their techniques, but found nothing.
Personally, I hope this study will involve continued monitoring over the decades until the wells are cemented in and abandoned. They have carefully created a baseline, and one should continue to look for changes. Modeling studies predict that it may take decades for contamination from a point source to reach sampling sites.4
Other locations may respond differently. But this study does show that the broad-brush hype that the anti-HF segment is mouthing is probably not universally true. If there is a problem with HF, it may distill down to location, location, location.
References
- http://www.netl.doe.gov/File%20Library/Research/onsite%20research/publications/NETL-TRS-3-2014_Greene-County-Site_20140915_1_1.pdf
- Ibid, Executive Summary, p. 1.
- Begos, K. Associated Press, Bay Area News Group, p. A7, Sept 17, 2014.
- Viswanathan, H. “Discovery Science of Hydraulic Fracturing: Innovative Working Fluids and Their Interactions With Rock, Fractures and Hydrocarbons. Lecture given at ACS Meeting, Aug 9, 2014, San Francisco, CA.
Robert L. Stevenson, Ph.D., is Editor, American Laboratory/Labcompare; e-mail: [email protected].