T91 Microbial Origin of Hydrocarbon Gases in Coal Beds and Sedimentary Basins

Monday, 29 October 2007
1:30 PM - 5:30 PM

CHARACTERIZATION OF THE BACTERIAL AND ARCHAEAL COMMUNITIES IN COALBED METHANE AQUIFERS IN THE WYODAK-ANDERSON COAL ZONE OF THE POWDER RIVER BASIN, WY USING POLAR LIPID ANALYSIS TECHNIQUES

Paper number: T91-3
Program: Technical Sessions
Time: 2:00 PM – 2:15 PM

Authors

Abstract

Bacterial and Archaeal community structure in the Wyodak-Anderson coal zone aquifer of the Powder River Basin, WY was examined by the analysis of Phospholipid Fatty Acids (PLFAs) and Phospholipid Ether Lipids (PLELs). Consistent with other studies of the deep subsurface, total microbial biomass sampled in coal bed methane (CBM) wells ranged from 9.7 x 105 cells/L to 6.4 x 108 cells/L, The Archaeal PLEL isoprenoids, phytane and biphytane, were detected in all wells across the basin. Biomass estimates derived from these PLEL measurements reveal a system dominated by Archaebacterial cells, which ranged from 78.2% to 99.8% of total biomass. The Archaea detected are likely methanogens, as confirmed by DNA analysis of two well samples and δ13C values as low as -60 ‰ for biphytane. Methanogenic lipid biomarkers were found in higher concentrations near the edge of the basin where aquifer recharge is suspected. Biomarkers suggestive of sulfate-reducing bacteria (SRB), including, 10me-16:0, cy-17, and i-17:1ω7c were also detected in six of the seven sampled CBM wells. Concentrations of 10me-16:0 and cy-17, whose co-occurence are indicative of the Desulfobacter genera of SRB, were also higher in the shallower CBM wells near the aquifer recharge zone.