Analysis of Gas Samples from Coalbed Methane Wells in Sullivan County, Indiana using Gas Chromatography
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Date
2016-12
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The Ohio State University
Abstract
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.
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Keywords
coalbed methane, Illinois Basin, hydrocarbon molecular composition, isotopic composition of methane