UNDERSTANDING STRAY GAS OCCURENCES IN SHALLOW AQUIFERS IN RANDOLPH COUNTY, WEST VIRGINIA, USA

With shale gas production rapidly increasing in the Appalachian basin, it’s important to characterize natural stray gas occurrences in shallow aquifers before hydrocarbon development expands. Enhanced understanding of relationships between stray gas occurrences and possible sources such as abandoned oil and gas wells, coalmines and natural faults and fractures is possible using isotopic and geochemical tools. Randolph County West Virginia is a region that has seen very little coal or natural gas development, but has high concentrations of stray gas as determined by a previous study from our research group. Previous results indicate up to 45 mg/L of methane occurring in a 98 m (320 ft) groundwater well completed in the Devonian Hampshire Formation. The surrounding region was targeted through intensive sampling (October-December 2013). The region overlies the southernmost portion of the Deer Park anticline and is in proximity to both a Precambrian basement and Devonian faults that run roughly NNE to SSW. The samples represent two main subsurface lithologies, a karst system as well as a predominantly siliclastic system. Samples were analyzed for dissolved gas composition, isotopes of dissolved methane, δ¹⁸O_H2O, δ²H_H2O, δ¹³C_DIC, alkalinity, cations, anions and standard field parameters. This study enhances the current understanding of natural stray gas occurrences through intensive sampling of residential and public groundwater wells in study area