Some important progress has been made in coalbed gas (CBG) exploration in the Kuqa-Bay coalfield in the northern Tarim Basin, where a demonstration base of CBG development and utilization has been established in the Tieliekedong (TD) region. Currently, there has been no detailed study of the formation mechanism of the CBG in the TD region, which has restricted the next phase of the CBG exploration. In this study, gas and water samples in the TD region were collected and analyzed to determine the genesis of the CBG, the formation pathways of the microbial gas, the source of the coalbed water, the composition of the microbial community, and the accumulation process of the CBG. The results indicate that the CBG in the TD region is a mixture of biodegraded thermogenic gas and secondary microbial gas. The geochemical characteristics of the water samples indicate that the coalbed water actively receives recharge from surface water, and it exhibits the characteristics of a weak-runoff water environment (i.e., a relatively closed system). Based on the stable isotope compositions of the gas-water samples, CO₂ reduction is the main metabolic pathway for generating the microbial gas. That is, in the relatively closed system, initial CO₂ from the different sources was converted to CH₄ by hydrogenotrophic methanogens (e.g., Methanobacterium), and the residual CO₂ became progressively enriched in ¹³C (i.e., high positive δ¹³C-CO₂ and δ¹³C-dissolved inorganic carbon values). However, the microbial community composition indicates that acetogenic bacteria (e.g., Acetobacterium, and Lentimicrobium) and acetoclastic methanogens (i.e., Methanosaeta) are widely developed in the coalbed water, so acetoclastic methanogenesis should also take place. According to the priority of the biodegradation, the microbial oxidation of thermogenic C₂₊ components (e.g., ethane and propane) mainly occurred in the early stage and lasted for a short period of time, primarily producing CH₄ enriched in ¹²C. After these components were consumed, the bacteria began to degrade the organic matter in the coal, and the methanogens continued to generate secondary microbial gas, finally forming a ¹³C-enriched pool of carbon species. Based on these results, the CBG accumulation in the TD region was determined. The results of this case study provide an obvious supplement to the geological theory of CBG accumulation, and have a guiding significance for CBG exploration in the TD region.

塔里木盆地北部库车湾煤田煤层气勘探取得重要进展，铁列克东地区建立了煤层气开发利用示范基地。目前，尚未对TD区CBG的形成机制进行详细研究，制约了下一阶段CBG的勘探。本研究通过采集和分析 TD 地区的气体和水样，确定了 CBG 的成因、微生物气体的形成途径、煤层水的来源、微生物群落的组成和成藏过程。 CBG 的。结果表明，TD区CBG是生物降解热成因气和次生微生物气的混合物。水样地球化学特征表明煤层水主动接受地表水补给，呈现出弱径流水环境（即相对封闭系统）的特征。基于气水样品的稳定同位素组成，CO₂还原是产生微生物气体的主要代谢途径。也就是说，在相对封闭的系统中，来自不同来源的初始CO ₂被氢营养产甲烷菌（例如甲烷杆菌）转化为CH ₄，并且残留的CO ₂逐渐富集¹³ C（即高正δ ¹³ C- CO ₂和 δ ¹³ C 溶解的无机碳值）。然而，微生物群落组成表明，产乙酸菌（例如，醋杆菌属和慢菌属）和产乙酸菌（例如，Methanosaeta ））在煤层水中广泛发育，因此也应该发生乙酸碎屑产甲烷作用。根据生物降解的优先顺​​序，产热C ₂₊组分（如乙烷和丙烷）的微生物氧化主要发生在早期，持续时间较短，主要产生富集¹² C的CH ₄ 。组分被消耗，细菌开始降解煤中的有机物，产甲烷菌继续产生次生微生物气体，最终形成¹³富含 C 的碳物种库。基于这些结果，确定了 TD 区域中的 CBG 积累。本案例研究结果对 CBG 成藏地质理论提供了明显的补充，对 TD 区 CBG 勘探具有指导意义。