Biomarker Indicators of Microbial Degradation of Organic Matter in the New Albany Shale
Steven Petsch1, Claire Astore1, Mark Woodworth1, Melissa Schlegel2, Jennifer McIntosh2, and Anna Martini3
1University of Massachusetts Amherst, Department of Geosciences, Amherst, MA 01003, [email protected], [email protected], [email protected]
2University of Arizona, Department of Hydrology and Water Resources, Tucson, AZ 85721, [email protected], [email protected]
3Amherst College, Department of Geology, Amherst, MA 01002, [email protected]
The New Albany Shale (Illinois Basin) is an active emerging shale gas reservoir, with geochemical and isotopic signatures of produced gas and water that support a partial microbial origin for the gas. Aliphatic and aromatic fractions of lipid extracts from multiple depths among three cores in the New Albany Shale, SW Indiana, were examined to assess the possible microbial degradation of organic matter. Molecular indicators reflect access of the methanegenerating microbial community to particular components of shale organic matter; vertical and lateral variations reflect the direction and intensity of microbial activity. Aliphatic hydrocarbons support moderate biodegradation throughout this gas shale. Aromatic hydrocarbons suggest more extensive biodegradation towards the base of the shale at shallow depths near the shale subcrop, but biodegradation becomes more pronounced in the upper Clegg Creek member with increasing depth in the basin. These observations are consistent with gas isotopic and compositional data from sidewall cores. These results indicate variability in the extent of microbial degradation over relatively short distances down core and may suggest locations of greater microbial activity that result from the complex hydrologic flow system in this basin.
AAPG Search and Discovery Article #90095©2009 AAPG Eastern Section Meeting, Evansville, Indiana, September 20-22, 2009