GSA Annual Meeting in Phoenix, Arizona, USA - 2019

Paper No. 182-11
Presentation Time: 9:00 AM-6:30 PM


ALVAREZ VILLA, Cristopher1, ERHARDT, Andrea M.1, FRYAR, Alan1, PARRIS, Thomas M.2, ZHU, Junfeng2 and WEBB, Steven E.2, (1)Earth and Environmental Sciences, University of Kentucky, 121 Washington Ave, 101 Slone Research Building, Lexington, KY 40506, (2)Kentucky Geological Survey, University of Kentucky, 228 Mining and Mineral Resources Building, Lexington, KY 40506

Elevated levels of methane (CH4) in groundwater can lead to accumulation of gas in enclosed areas, resulting in potentially explosive environments. A recent study in northeastern Kentucky identified dissolved methane to be a widespread phenomenon, with 28% (n= 51) of analyzed domestic wells in the “warning” and “immediate action” level ranges. The wells with nearby mining activities were more likely to have elevated methane levels (CH4 > 1 mg/L). In contrast, a study in southeastern Kentucky observed significantly lower concentrations and an inverse correlation between CH4 concentration and proximity to mining activities. CH4 concentrations showed no correlation with distance to oil and gas wells in either study. However, recent evaluations of horizontal drilling and hydraulic fracturing as options to develop two major oil and gas plays in eastern Kentucky have increased interest in understanding baseline groundwater chemistry in the overlying shallow Pennsylvanian sandstone aquifers. Furthermore, even though large variations in chemical and isotopic composition observed over short distances are consistent with a dissected topography and limited hydrologic communication, local trends in chemical parameters and different solute availability could explain some of the observed differences in CH4 concentrations. We sampled 18 groundwater wells for bulk chemistry and isotopic composition in an unanalyzed region located between previous studies. Initial results of major cations, anions, dissolved gas concentrations, δ13CDIC, δ2H, δ18O, δ13CCH4 and δ2HCH4 suggest a biogenic source of methane for wells where sulfate (SO42-) concentrations are low. δ34SSO4 and δ18OSO4 data should elucidate sulfate sources for a subset of wells with high sulfate. Additionally, we compile and show trends in chemical and isotopic composition of groundwater in Eastern Kentucky and how they relate to methane concentrations. Further geospatial and statistical analysis of data in relation to anthropogenic activities (mining, oil and gas development) should elucidate methane and sulfate dynamics and any geochemical processes associated. We anticipate this study to improve our understanding of groundwater geochemical zones and processes, as well as the effects of previous and future resource development in Eastern Kentucky.