부산대학교 도서관

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.orggeochem.2006.09.005 Byline: Dariusz StrApoA (a), Maria Mastalerz (b), Cortland Eble (c), Arndt Schimmelmann (a) Abstract: Coalbed gases and waters from exploratory and production gas wells in the southeastern Illinois Basin were sampled to assess geochemically the origin of coalbed gases, with an emphasis on the Springfield and Seelyville Coal Members that are commercially targeted for coalbed methane production in Indiana. On-line analyses of hydrocarbon gases methane to butanes (C.sub.1, C.sub.2, C.sub.3, n-C.sub.4, i-C.sub.4) and CO.sub.2 yielded gas concentrations, plus [delta]D and [delta].sup.13C values. The low thermal maturity of Indiana coals with vitrinite reflectance R.sub.0 [approximately equal to]0.6% is in agreement with an overwhelmingly biogenic isotopic signature of coalbed gases containing [greater than or equal to]96% methane generated via bacterial CO.sub.2-reduction. In contrast, thermogenic gas was generated in the stratigraphically equivalent coal beds in western Kentucky's Rough Creek Graben zone where higher maturities of up to R.sub.0 [approximately equal to]0.8% were reached owing to tectonic and hydrothermal activity. No secondary biogenic methane was observed in more mature western Kentucky coal beds where greater burial depth limits the recharge of meteoric water. Biogenic and thermogenic coalbed gases represent two end-members that are compositionally and isotopically distinct. Microbial biodegradation of thermogenic C.sub.2+ hydrocarbon gases in Indiana coal beds preferentially targets C.sub.3 and introduces isotope fractionation whereby remaining C.sub.3 is enriched in deuterium and.sup.13C. Author Affiliation: (a) Department of Geological Sciences, Indiana University, 1001E 10th Street, Bloomington, IN 47405-1405, USA (b) Indiana Geological Survey, Indiana University, 611 N. Walnut Grove, Bloomington, IN 47405, USA (c) Kentucky Geological Survey, University of Kentucky, Lexington, KY 40506, USA Article History: Received 10 July 2006; Revised 13 September 2006; Accepted 15 September 2006 Article Note: (miscellaneous) Associate Editor -- C.C. Walters