Potential and Constraints of Biogenic Methane Generation from Coals and Mudstones from Huaibei Coalfield, Eastern China

Abstract

Coalbed methane (CBM) resources formed biogenically and thermogenically have been discovered in the Permian coalbeds of the Huaibei coalfield. Four coals, three mudstones, and five coalbed-produced water samples collected from the Linhuan, Luling, and Haizi coal mines of the Huaibei coalfield were characterized geochemically and biologically to gain an understanding of the biogenic methane generation potential and the microbial communities involved in situ and in coalbed-produced water-enriched samples. The 16S rRNA gene high-throughput sequencing results showed that the archaeal communities from in situ and enriched cultures were dominated by Methanolobus and Methanobacterium species. The organic material of coals and mudstones could be biodegraded under an anaerobic incubation. The maximum biogenic methane generation potentials of coal and mudstones were 98.5 and 72.5 μmol/g within 123 days, respectively. Volatile matter and total organic carbon (TOC) content were the most important internal factors affecting biogenic methane generation from coals and mudstones. The Na-SO 4 water type resulted in a low methane generation potential.

Biogeochemistry and the associated redox signature of co-produced water from coalbed methane wells in the Shizhuangnan block in the southern Qinshui Basin, China

“…This supports the hypothesis that sulfate reduction by sulfate-reducing bacteria inhibits methanogenesis (Jones et al., 2010). Meanwhile, the region with highest δ 13 C DIC values and negligible SO 4 2– concentrations only relates to low production wells, indicating that the most reductive environments are too strict to allow extension of pressure drop funnels and support fluid migration (Bao et al., 2019). Importantly, the output of these wells can potentially be increased by effective measures such as hydraulic fracturing (Hou et al., 2017).…”

Gas geochemistry and hydrochemical analysis of CBM origin and accumulation in the Tucheng syncline in western Guizhou Province

“…Schlegel et al (2011) pointed out that a reduced environment with Eh <200mV, rich in organic matter and circumneutral pH value (pH=4~9), was conducive to generation of biogenic gas. In underground water, changes in dissolved inorganic carbon (DIC) can reveal the biogeochemical behavior of carbon, with positive δ 13 C-DIC values usually associated with methanogenesis in organic matter-rich systems (Bao et al, 2019;Guo et al, 2012). As cases in point, the δ 13 C-DIC values of coal-based water in the Huaibei coalfield, China; the Black Warrior Basin, USA; and the Powder River Basin, USA, are 21.1‰~26.0‰, 2.8‰~13.1‰, and 12.0‰~22.0‰, respectively, and biogenic methane has been identified in all three (McIntosh et al, 2008;Sharma and Frost, 2008;Li et al, 2015a).…”

Biogeochemistry and Water–Rock Interactions of Coalbed Methane Co-Produced Water in the Shizhuangnan Block of the Southern Qinshui Basin, China

“…Combining the species diversity results in Table 2 and the hydraulic head (H) levels in Table 1, the bacterial community including sulfate reducing bacteria at shallow hydraulic head were found to be more abundantly diverse than at deep hydraulic head due to the higher SO4 2− concentrations. Similarly, the archaeal community including methanogens were more abundantly diverse at deep hydraulic head than at shallow hydraulic head, resulting from the depletion of SO4 2− concentrations [46]. The sequencing results including reads, operational taxonomic units (OTUs), Chao index, Ace index, Shannon index, and Simpson index values from the six water samples are shown in Table 2.…”