A GEOCHEMICAL AND ISOTOPIC STUDY OF STRAY GAS RELATED TO STRUCTURAL AND TOPOGRAPHIC FEATURES IN THE SOUTHERN APPALACHIAN BASIN

The accurate characterization of sources and distribution of dissolved methane (commonly referred to as stray gas) is imperative as shale gas production rapidly increases in basins around the world, including the Appalachian basin. With public awareness and concern about stray gas incidents on the rise, a complete understanding of spatial baseline concentrations and their relationships with abandoned oil and gas wells, coal mines and natural faults and fractures is necessary. Geochemical and isotopic characterization of the dissolved gas accompanied by water geochemistry can help identify potential sources of stray gas and mixing/migration trends. Previous results from a groundwater study conducted by our research group in the Appalachian basin found high concentrations of methane (> 45 mg/L) occurring in shallow aquifers in Randolph County, West Virginia (Mulder, 2012). The sample with the highest concentration collected during the study was taken from a well 320 feet (97m) deep in the Devonian Hampshire Formation. A thorough follow-up sampling of groundwater will target areas with basement faults as well as topographic lows as these two particular settings are hypothesized to create ideal conditions for stray gas to migrate from depth. This study better establishes baseline conditions of naturally occurring stray gas related to structural and topographic features.