Distribution characteristics of C-N-S microorganism genes in different
hydraulic zones of high rank coal reservoirs in southern Qinshui Basin
Wei SHI a,b,c,
Shuheng TANG a,b,c11*Corresponding author, e-mail: tangsh@cugb.edu.cn , Wenhui HUANGa,b,c, Songhang ZHANG a,b,c,
Zhongcheng LI d
a. MOE Key Lab of Marine Reservoir Evolution and Hydrocarbon Enrichment
Mechanism, Beijing 100083, China
b. MOLR Key Lab of Shale Gas Resources Survey and Strategic Evaluation,
Beijing 100083,China;
c. School of Energy Resources, China University of Geosciences
(Beijing), Beijing 100083, China
d. China United Coalbed Methane Corporation Ltd., Beijing 100011, China
Abstract: Microbial decomposition of carbon and biogenic
methane in coal is one of the most important issues in CBM exploration.
Microbial C-N-S functional genes in different hydraulic zones of high
rank coal reservoirs was studied, demonstrating high sensitivity of this
ecosystem to hydrodynamic conditions. The results shows that
hydrodynamic strength of the 3# coal reservoir in Shizhuangnan block
gradually weakened from east to west, forming the transition feature
from runoff area to stagnant area. Compared with runoff area, the
stagnant area has higher reservoir pressure, gas content and ion
concentrations. The relative abundance of genes associated to C, N and S
cycling was increased from the runoff area to stagnant area, including
cellulose degrading genes, methane metabolism genes, N cycling genes and
S cycling genes. This indicates that the stagnant zone had more active
microbial C-N-S cycle. The machine learning model shows that these
significantly different genes could be used as effective index to
distinguish runoff area and stagnant area. Carbon and hydrogen isotopes
indicate that methane in the study area was thermally generated. The
methanogens compete with anaerobic heterotrophic bacteria to metabolize
limited substrates, resulting in low abundance of methanogens.
Meanwhile, the existence of methane oxidizing bacteria suggests biogenic
methane was consumed by methanotrophic bacteria, which is the main
reason why biogenic methane in the study area was not effectively
preserved. In addition, weakened
hydrodynamic conditions increased genes involved in nutrient cycling
contributed to the increase of CO2 and consumption of
sulfate and nitrate from runoff area to stagnant area.
Keywords: coal bed methane; hydraulic zones; C-N-S
microorganisms; genes; coal; water