Abstract: Microbial synergistic metabolism drives carbon cycle processes such as organic matter degradation and CO₂ reduction, offering novel insights for the green development of coal resources and the utilization of geological carbon sequestration. Clarifying the distribution, metabolism, and environmental drivers of carbon-cycling microbial communities in regional in-situ ecosystems is critical for enhancing and guiding the metabolic efficiency and pathways of hydrogenotrophic methanogens in coal reservoirs. Focusing on Shizhuangnan Block in southern Qinshui Basin, reservoir water samples collected during non-rainy seasons were analyzed using bio-sequencing, functional prediction, and statistical methods to investigate microbial community characteristics, metabolic potential, and influencing factors. Results revealed Proteobacteria, Acidobacteria, Actinobacteria, Bacteroidetes, Chloroflexi, Firmicutes, Nitrospirae, and Spirochaetes as dominant bacterial phyla, with Euryarchaeota being the predominant archaeal phylum. Bacterial community distribution and diversity were influenced by environmental factors such as Total Dissolved Solids (TDS) and Total Organic Carbon (TOC), while archaeal communities showed weaker environmental sensitivity. Comparative analysis of microbial functional genes across hydrological units demonstrated that environmental factors jointly drive microbial symbiosis in carbon and other biogeochemical cycles. Key enzyme gene abundances related to organic degradation and methane metabolism were significantly higher in the northwestern stagnant zone than in the southeastern runoff zone. Gene abundance of carbon fixation pathways in methanogenic archaea was elevated in stagnant zones, regulated by Dissolved Oxygen (DO), Oxidation Reduction Potential (ORP), TDS, TOC, and \mathrmSO_4^2- . The study reveals the metabolic functional potential of in-situ coal reservoirs for enhanced biogas production and CO₂ bio-utilization through hydrogenotrophic methanogens, along with their environmental regulatory mechanisms, providing theoretical basis and data support for site selection or reservoir modification in fossil energy bioengineering field practices.