Microbiome of High-Rank Coal Reservoirs in the High-Production Areas of the Southern Qinshui Basin

Wei Shi; Shuheng Tang; Songhang Zhang

doi:10.3390/microorganisms11020497

Microbiome of High-Rank Coal Reservoirs in the High-Production Areas of the Southern Qinshui Basin

Microorganisms. 2023 Feb 16;11(2):497. doi: 10.3390/microorganisms11020497.

Authors

Wei Shi^{1

2

3}, Shuheng Tang^{1

2

3}, Songhang Zhang^{1

2

3}

Affiliations

¹ MOE Key Lab of Marine Reservoir Evolution and Hydrocarbon Enrichment Mechanism, Beijing 100083, China.
² MOLR Key Lab of Shale Gas Resources Survey and Strategic Evaluation, Beijing 100083, China.
³ School of Energy Resources, China University of Geosciences (Beijing), Beijing 100083, China.

Abstract

To study the distribution features of microorganisms in distinct hydrological areas of the southern Qinshui Basin, C-N-S microorganisms were studied using 16S RNA sequencing, metagenome sequencing and geochemical technologies, showing the high sensitivity of microorganisms to the hydrodynamic dynamics of coal. The hydrodynamic intensity of the #3 coal gradually decreased from the runoff areas to the stagnant areas. The stagnant zones have higher reservoir pressure, methane content, δ¹³C_DIC and TDS and lower SO₄^2-, Fe³⁺ and NO₃^- concentrations than the runoff areas. C-N-S-cycling microorganisms, including those engaged in methanogenesis, nitrate respiration, fermentation, nitrate reduction, dark oxidation of sulfur compounds, sulfate respiration, iron respiration, chlorate reduction, aromatic compound degradation, denitrification, ammonification and nitrogen fixation, were more abundant in the stagnant areas. The relative abundance of C-N-S functional genes, including genes related to C metabolism (e.g., mcr, mer, mtr, fwd and mtd), N metabolism (e.g., nifDKH, nirK, narGHI, nosZ, amoB, norC and napAB) and sulfur metabolism (e.g., dsrAB and PAPSS), increased in the stagnant zones, indicating that there was active microbiological C-N-S cycling in the stagnant areas. The degradation and fermentation of terrestrial plant organic carbon and coal seam organic matter could provide substrates for methanogens, while nitrogen fixation and nitrification can provide nitrogen for methanogens, which are all favorable factors for stronger methanogenesis in stagnant areas. The coal in the study area is currently in the secondary biogenic gas generation stage because of the rising of the strata, which recharges atmospheric precipitation. The random forest model shows that the abundance of C-N-S microorganisms and genes could be used to distinguish different hydrological zones in coal reservoirs. Since stagnant zones are usually high-gas-bearing zones and high-production areas of CBM exploration, these microbiological indicators can be used as effective parameters to identify high-production-potential zones. In addition, nitrate respiration and sulfate respiration microorganisms consumed NO₃^- and SO₄^2-, causing a decrease in the content of these two ions in the stagnant areas.

Keywords: C-N-S microorganisms; coalbed methane; hydraulic zones; southern Qinshui Basin.

Grants and funding

This study was supported by the NSFC-Shanxi Coal-based Low Carbon Joint Fund of China (grant number U1910205) and the National Natural Science Foundation of China (grant numbers 41872178, 41772159).