Characterization of the origin of coalbed gases in southeastern Illinois Basin by compound-specific carbon and hydrogen stable isotope ratios

摘要: Abstract Coalbed gases and waters from exploratory production gas wells in the southeastern Illinois Basin were sampled to assess geochemically origin of coalbed gases, with an emphasis on Springfield Seelyville Coal Members that are commercially targeted for methane Indiana. On-line analyses hydrocarbon butanes (C 1 , C 2 3 n -C 4 i ) CO yielded concentrations, plus δ D 13 values. The low thermal maturity Indiana coals vitrinite reflectance R 0  ∼ 0.6% is agreement overwhelmingly biogenic isotopic signature containing ⩾96% generated via bacterial -reduction. In contrast, thermogenic was stratigraphically equivalent coal beds western Kentucky’s Rough Creek Graben zone where higher maturities up  ∼ 0.8% reached owing tectonic hydrothermal activity. No secondary observed more mature Kentucky greater burial depth limits recharge meteoric water. Biogenic represent two end-members compositionally isotopically distinct. Microbial biodegradation 2+ preferentially targets introduces isotope fractionation whereby remaining enriched deuterium C.