3 Environmental Problems and Solutions Associated with Appalachian Shale Plays and Coal Mining

Thursday, 12 April 2018
8:00 AM - 12:00 PM
Room 300 D

NO DIRECT EVIDENCE OF METHANE IN SHALLOW GROUNDWATER FROM HYDRAULIC FRACTURING ACTIVITIES IN EASTERN KENTUCKY

Paper number: 3-8
Program: Theme Sessions
Time: 10:10 AM – 10:30 AM

Authors

Abstract

Previous research has demonstrated that hydraulic fracturing has the potential to contaminate shallow aquifers with methane (CH4) from deeper formations. This study compares concentrations and isotopic compositions of CH4 sampled from domestic groundwater wells in Letcher County, Eastern Kentucky in order to characterize its relation to neighboring hydraulically fractured natural gas wells. The studied groundwater shows elevated CH4 concentrations ranging from 0.05 mg/L to 10 mg/L (mean: 4.92 mg/L). However, this is considerably lower compared to the northern Appalachian Basin (e.g., Marcellus Shale) where the CH4 concentrations reach as high as 70 mg/L. The measured δ13C values of CH4 range from -66 ‰ to -16 ‰ (mean: -46 ‰), and δ2H values range from -286 ‰ to -86 ‰ (mean -204 ‰). The occurrence of CH4 is not correlated with proximity to hydraulically fractured natural gas wells. Generally, CH4 occurrence corresponds with Na-Cl-HCO3-rich and more reducing groundwater, and with low concentrations of SO4. Additionally, groundwater in greater proximity to surface mining is more likely to be oxidized and contains less CH4. We infer that mining activities increase the probability of CH4 oxidation in shallow groundwater of Letcher County. Our results suggest that hydraulic fracturing does not increase the likelihood of stray gas migration into the groundwater of eastern Kentucky, although CH4 concentrations can be elevated in this region. Local residents have reported occasional accidents of domestic well combustion as a result of excessive CH4 accumulation. The isotopic values of CH4 suggest an immature thermogenic and mixed biogenic/thermogenic origin rather than thermogenically mature shale gas. More research is needed to explain the distribution of CH4 concentrations. Future studies should include more intensive sampling within a smaller area as the region's mountainous terrain creates relatively isolated valleys, making the chemical and isotopic results spatially heterogeneous.

Geological Society of America Abstracts with Programs. Vol. 50, No. 3

doi: 10.1130/abs/2018SE-312203

© Copyright 2018 The Geological Society of America (GSA), all rights reserved. Permission is hereby granted to the author(s) of this abstract to reproduce and distribute it freely, for noncommercial purposes. Permission is hereby granted to any individual scientist to download a single copy of this electronic file and reproduce up to 20 paper copies for noncommercial purposes advancing science and education, including classroom use, providing all reproductions include the complete content shown here, including the author information. All other forms of reproduction and/or transmittal are prohibited without written permission from GSA Copyright Permissions.