Coalbed gas origin and distribution in the southeastern Illinois Basin

Coal seams worldwide contain biogenic methane that in some coal basins forms easily accessible and large amounts of coalbed methane (CBM). Economically important biogenic CBM occurs not only in coals of low rank but also in higher rank coals where uplift and brine dilution initiated microbial methanogenesis. Distributions and compositions of gases in biogenic systems are governed by numerous factors including salinity, microbe-accessible porosity, and coal permeability. In contrast, thermogenic gas systems are primarily controlled by coal rank and depth. Determination of gas origin is, therefore, critical for a successful exploration strategy. This study employs geochemical, stable isotopic, and microbiological techniques to investigate the distribution and the origin of coalbed gases in the southeastern Illinois Basin. Our results suggest that high permeability and shallow (100-250 m) depths of Indiana coals allowed their inoculation with a methanogenic microbial consortia, thus leading to widespread and abundant microbial methane generation along the eastern marginal part of the Illinois Basin. Consequently, high volatile bituminous C Indiana coals with a vitrinite reflectance Ro ~ 0.6% contain significant amounts of coal gas (~3 cm3/g, 96 scf/t) with ≥ 97 vol.% of microbial methane. In contrast, deeper (>300 m) and more mature (high volatile bituminous A) coals in a tectonically active zone in the western Kentucky part of the basin contain gases of distinctly thermogenic origin. Enrichment experiments and phylogeny of the microbial community responsible for generation of coalbed methane in the Indiana part of the Illinois Basin imply that coal organic matter was biodegraded by a complex microbial consortium to form simple molecules, such as H2 and CO2, that fuel methanogenesis. 16S rRNA analyses of both in-situ microbial communities and methanogen enrichments indicate that Methanocorpusculum is the dominant genus responsible for biogenic CBM formation.

Grantor dc:publisher

[Bloomington, Ind.] : Indiana University

Year dc:date.issued

2010

Author dc:creator

• Strapoc, Dariusz

Advisors dc:contributor.advisor

• Scimmelmann, Arndt
• Mastalerz, Maria

Language dc:language.iso

EN

Handle dc:identifier.uri

https://hdl.handle.net/2022/7465

OAI identifier oai:identifier

oai:scholarworks.iu.edu:2022/7465