Dissolved Methane in Fresh-Water Aquifers in the Footprint of Some Texas Shale Plays
Bureau of Economic Geology, The University of Texas at Austin
Many constituents typically associated with oil and gas production, such as methane and higher-order alkanes, exist naturally in shallow groundwater. Recent studies of aquifers in the footprint of several gas plays across the US have showed that (1) dissolved thermogenic methane may or may not be present in the shallow subsurface and (2) shallow thermogenic methane could be naturally occurring and emplaced through mostly vertical migration over geologic times and (3) dissolved methane is not necessarily a consequence of gas production from a gas play.
In a recent DOE-funded project, we sampled 800+ water wells across the state of Texas to characterize shallow methane in fresh-water aquifers overlying shale plays (Barnett, Eagle Ford, Haynesville shale areas) as well as in the Delaware Basin of West Texas. Results suggest that, although not uncommon, dissolved methane is not widespread in shallow Texas groundwaters. When present at concentrations >10 mg/L, dissolved methane is sometimes of thermogenic or mixed origin but likely from a natural source.
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