EAST TENNESSEE GEOLOGICAL SOCIETY
  OCTOBER 2014


Monday, October 13, 2014
6:00 - 7:30 pm

Pellissippi State Technical Community College
10915 Hardin Valley Road, Knoxville
J.L. Goins Administration Building, Cafeteria Annex

OCTOBER PRESENTATION

Characterizing Groundwater Alteration by Hydraulic Fracturing
Using Radionuclides and Stable Isotopes

By
St. Thomas LeDoux, MS Candidate
University of Tennessee
Department of Earth and Planetary Sciences

Knoxville, Tennessee

Each year the Department of Earth and Planetary Sciences at UTK offers a course on Professional Presentations (Geology 596) to provide a formal opportunity for students to develop their oral communication skills. This one-credit course involves writing an abstract and preparing, practicing, and delivering a 15-minute professional presentation on any geological topic of interest, usually a portion of their thesis/dissertation research. The students present their talks at a departmental seminar and are ranked by the faculty. This year ETGS has partnered with UTK to further broaden this valuable experience by recognizing the best Masters- and best Doctoral-student presentations and inviting them to reprise their talks.

The winners this year were St. Thomas LeDoux (best Masters presentation) and Nicole Lunning (best Doctoral presentation).  Nicole gave her talk: "Insights from Regolithic Meteorites and a Discussion of Meteorites from Antarctica," during the May Meeting. St. Thomas, who was unable to attend our May meeting because of a prior commitment, has agreed to do an ETGS talk this month.The abstract of his talk are given below.  

  Abstract

Hydraulic fracturing used for shale gas extraction has garnered a great deal of attention and criticism regarding its potential to pollute shallow groundwater and surface water. Over the past decade, several studies have shown that hydraulic fracturing may cause contamination of groundwater and/or surface water. However, the broader scientific literature on this subject is still limited in terms of methodological scope and geographic context, and has been focused primarily on conventional, water-based hydraulic fracturing techniques implemented in the Marcellus Shale region of western Pennsylvania, USA. As a result, the applicability of these findings in alternative shale gas plays—e.g., the shallower Chattanooga Shale, which is fractured using nitrogen foam instead of water—remains largely untested.

This study characterizes groundwater in Letcher County, Kentucky, USA using chemical and isotopic tracers to identify indicators of water pollution from hydraulic fracturing in the Chattanooga Shale. Groundwater samples collected from private drinking water wells have been analyzed for: 1) concentrations of major ions, metals, methane gas, and radon gas; 2) δ13C and δ2H composition of CH4; and 3) δ34S and δ18O composition of SO4. Results from these analyses have been analyzed for each sample site using multiple regression to determine correlations between drinking well water composition and proximity to hydraulically fractured shale gas wells. The methods and analyses implemented in this study are meant to largely mimic previous research in the Marcellus Shale region to verify its applicability in shallower drilling contexts that use less hydraulically-intensive methods to fracture shale deposits.

The chemical composition of the studied groundwater from the Chattanooga Shale has shown different variations compared to the Marcellus Shale. Concentrations of methane gas have shown to marginally increase with proximity to the hydraulically fractured shale gas wells. In contrast, concentrations of radon gas have not exhibited a pattern as a function of proximity to hydraulically fractured wells. The wide variation of δ34S in dissolved sulfate (-1.2 to +34.3%) suggests mixing processes between waters of different origin and/or subsequent alteration by microbial sulfate reduction.

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