NEW ALBANY SHALE MICROBIOLOGY AND GEOCHEMISTRY: CHARACTERIZATION OF AND GEOCHEMICAL CONSTRAINTS ON METHANE GENERATING MICROBIAL COMMUNITIES

The New Albany Shale is the largest shale gas play in the United States by area, covering nearly 43,500 square miles in the Illinois Basin. The shale’s eastern margin in Indiana and Kentucky contains substantial natural gas reserves of microbial origin. An active methanogenic community exists due to dilute formation waters and low levels of competing terminal electron accepting metabolic reactions such as bacterial sulfate reduction. Geochemical and isotopic analyses of about 30 formation water and gas samples from natural gas wells in Western and Southern Indiana suggest that a significant portion of extracted natural gas is produced by methanogens. Specifically, δ¹³C values of methane and carbon dioxide along with δD values of methane and water indicate that methanogenesis largely occurs through a carbon dioxide-reduction pathway. Water samples were also collected for microbial community determination. Morphological diversity was assessed through direct counts and fluorescent in-situ hybridization (FISH) of filter-extracted cells collected from formation waters. Genes encoding 16S rRNA were extracted, amplified, and sequenced to produce archaeal and bacterial molecular phylogenies. Terminal restriction fragment length polymorphism (TRFLP) was also used to characterize the variety of metabolic pathways represented in microbiological samples. Comparison to data from the Antrim Shale of northern Michigan will indicate the geographic variation between methanogenic communities inhabiting organic-rich black shales permeated with dilute glacial waters.