Stable Isotopic and Geochemical Spatial Analysis of Surface Waters in an Area of Rapidly Expanding Marcellus Shale Development in the Monongahela River Basin of West Virginia
Pelak, Adam J.; Sharma, Shikha
Development of the Marcellus Shale gas play in the Monongahela River basin of north-central West Virginia has been intensifying over the past several years. Hydraulic fracturing is a technique to achieve economic gas production from the Marcellus Shale, and presents several possible sources of contamination to surface waters and groundwaters. During hydraulic fracturing a mix of water, sand and chemicals is injected thousands of feet underground under high pressure, breaking up shale formations to release trapped gas. The fluids that are injected in to the target formation are returned to the surface as flowback water. Flowback water can potentially contain toxic chemicals and highly saline brines. Leaky storage ponds, accidents involving transportation of water, and improper disposal of flowback water have the potential to contaminate surface waters in areas of shale gas development. This study was designed to document the stable isotopic and geochemical variations in 50 surface water sample sites in the Monongahela River basin in West Virginia. Sample sites were chosen by identifying all HUC-12 watersheds in the Monongahela River basin in West Virginia, then sub-dividing the watersheds in to five categories of Marcellus Shale development. Sample site watersheds range in size of drainage basin from 10.4 mi2 to 39.8 mi2. The five categories of Marcellus Shale development are; high production, low production, near high production, near low production, and no production that is underlain by Marcellus Shale greater than 50 feet thick. Width-integrated samples were collected at each site and were analyzed for major-ion chemistry, trace elements, radiochemistry, isotopic composition of water (δ18OH2O, δ2HH2O), DIC (δ13CDIC), dissolved sulfate (δ34SSO4, δ18OSO4), and field parameters of temperature, pH, conductivity, dissolved oxygen, turbidity, and alkalinity. All samples were collected at baseflow to ensure all contributions to surface water are from groundwater. Stable isotopic and geochemical results are used in statistical and spatial analyses in ArcGIS 10.0 to compare the 5 different stages of Marcellus Shale production in the Monongahela River basin. Establishing these geochemical and isotopic conditions at baseflow will allow for understanding of potential impacts to water quality as this area undergoes rapid expansion of shale gas development.
AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013