Analysis of Gas Samples from Coalbed Methane Wells in Sullivan County, Indiana using Gas Chromatography

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The Ohio State University

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Although there has been an increase in natural gas production from coalbed methane (CBM) reservoirs in the past few decades, there are multiple inadequately known aspects of CBM reserves. To understand the systematics of CBM production, twenty gas samples were collected from producing coalbed methane wells in Sullivan County, Indiana. These wells are producing from the Springfield and Seelyville coal seam units in the Illinois Basin and have been characterized for their noble gas chemistry previously. Here, the hydrocarbon molecular composition, isotopic composition of carbon and hydrogen in methane, and major gas composition (N2, CO2) are reported. One of the goals of this experiment is to use the composition of produced gases to determine the relative proportions of major inert gases compared to economically viable hydrocarbon gases. Another goal of this thesis is to use the composition of the produced gases to determine if natural gas formation in coal seams in the Illinois Basin is formed by biogenic processes or thermogenic processes. Based on the analyses conducted in this experiment, it appears that the wells have a dry gas composition (<1% ethane plus) and contain 2.7 to 10.6% non-hydrocarbon gases (N2, CO2). Based on the presence of ethane in the majority of wells, one can conclude that there is a mixture of biogenic and thermogenic natural gas forming in the Springfield and Seelyville coal seams.



coalbed methane, Illinois Basin, hydrocarbon molecular composition, isotopic composition of methane