AMBIENT GEOCHEMICAL AND ISOTOPIC VARIATIONS IN WATERS OF AN AREA OF ACCELERATING MARCELLUS SHALE GAS DEVELOPMENT

One of the most challenging issues associated with Marcellus shale gas drilling is to ensure proper management and disposal of flowback water produced as a result of hydraulic fracturing of gas wells. The flowback water consists of a mixture of returned fracking fluids and highly saline formation brines. Therefore, its improper management or disposal can potentially contaminate the fresh surface waters and groundwaters of the area. However, to better assess any detrimental effect on water quality there is need to understand the ambient natural temporal and spatial geochemical variations in the area. This study focuses on documenting the baseline geochemical characteristics of the groundwaters in different formations lying stratigraphically above the Marcellus formation. Water samples are being collected from approximately 40 groundwater wells in the north-central West Virginia, where Marcellus shale drilling is projected to rapidly expand in the coming two years. The variety of public and private well locations represents different formation aquifers and differing well depths. These include the Allegheny, Chemung, Conemaugh, Dunkard, Greenbrier, Kanawha, Monongahela, New River, Pocono, and Upper-Middle Devonian Series. Geochemical data will be obtained for cations and anions, trace elements, dissolved gas concentrations of methane, oxygen, nitrogen, argon, and carbon dioxide, oxygen and hydrogen isotopic composition of water (δ¹⁸O_H2O and δD_H2O), carbon isotopic composition of dissolved inorganic carbon (δ¹³C_DIC), sulfur and oxygen isotope composition of dissolved sulfate (δ³⁴S_SO4 and δ¹⁸O_SO4), and carbon and hydrogen isotope composition of dissolved methane (δ¹³C_CH4 and δD_CH4). Field parameters of temperature, conductivity, pH, dissolved oxygen, turbidity, and oxidation reduction potential will also be determined. We hypothesize that baseline geochemical variations documented in this study can be used to understand the impact of future shale gas development on the water quality of groundwater aquifers of this area.