Characteristics of biological gas production and microbial metabolism in coal seams on the eastern margin of the Ordos Basin

As coalbed methane wells in the eastern margin of the Ordos Basin have the problem of production decline that occurs in the middle and later stages, this study explores the adoption of biological stimulation technology as a potential stimulation measures. By collecting the produced fluid from low-yield wells as the bacterial source and conducting biological gas production simulation experiments in combination with coal samples,the variation characteristics of parameters such as metabolic intermediate products, key enzyme activities, microbial community structure and functional metabolic pathways were systematically analyzed. The experimental results show that the coal sample has a certain methane production potential under the activation conditions of bacterial sources in low-yield wells,and the methane yield per unit mass of coal reaches 1. 15 mL/g. Microorganisms degraded organicsubstrates in coal to produce intermediate products such as organic acids,alcohols and H2. The acidic substances serving as substrates for methanogens are promptly degraded and interconverted in the system. The activities of coenzyme F420,hydrogenase,and cellulase are consistent with the changing trend of biological gas production,while the metabolic activities of related microorganisms underwent concurrent changes. In the gas production system,pseudomonas accounted for 57%, while methanococcus and methanofollis are dominant,with a combined proportion exceeding 98%. Bacterial diversity is higher than that of archaea,and they jointly participate in the degradation and transformation of macromolecular substances in coal. In the process of biological gas production,methanogenic bacteria are involved in three pathways of methane metabolism,maximizing the efficiency of methane production. The production of acetotrophic methane accounted for 51. 5%,while the production of hydrogentrophic and methyl-trophic methane accounted for 30. 4% and 18. 1% respectively. The dominant archaeal flora in the fermentation system can participate in different methane synthesis pathways and eventually produce biomethane.