Hydrogeochemical Evolution of Basinal Fluids in the Paradox Basin: Implications for Sources, Paleofluid Flow, and Water-Rock Interations

Burial and Denudation Alter Microbial Life at the Bottom of the Hypo‐Critical Zone

“…Reviewing the literature, natural gas accumulations in Permian through Eocene reservoirs, in the Paradox and Uinta basins, associated with and without oil, all contain thermogenic gases formed as the basins subsided (Kim, 2022; Zhang et al., 2009), providing further evidence of relatively high temperatures and sterilization during maximum burial. More recent microbial activity has overprinted several of the shallow reservoirs with microbial methane from degradation of coal, shale, oil, or natural gas, presumably following uplift and erosion.…”

“…There is a trace of microbial methane and evidence of oxidation of thermogenic gases in deeper Honaker Trail and Cutler Fm reservoirs along the southeastern margin of the Paradox Basin near the Uncompahgre Uplift (Kim, 2022). Previous studies have shown that these deeper reservoirs (up to 2.2 km), above the Paradox Fm evaporites, were partially flushed by meteoric recharge within the last ∼800 ka (Kim, Ferguson, et al., 2022; Tyne et al., 2022).…”

“…Removal of CH 4 and/or longer chain HCs via anaerobic microbial oxidation imparts a strong 13 C‐enrichment in the remaining HCs; for example, relatively high δ 13 C values of ethane (C 2 ) and propane (C 3 ) (McIntosh et al., 2019). Clumped isotopes of methane that are out of equilibrium, with anomalously high Δ 13 CH 3 D, can also indicate microbial methane oxidation (Kim, 2022). CO 2 and resultant dissolved inorganic carbon (DIC), produced from BSR or bacterial iron reduction coupled to HC oxidation, has δ 13 C values similar to the organic matter source.…”