差异煤阶次生生物气生成演化特征及微生物作用机制

Since the secondary biogenic coalbed methane was discovered at the San Juan basin, the contribution of secondary biogenic gas on CBM is arousing the concern worldwide. While there is less systematically study on the diversity of microbe, characteristic and mechanism of secondary biogenic coalbed methane generation from coal samples with different coal rank. Based on the collection of vast coal samples and associated water samples, the experiments of methanogens domestication and enrichment cultivation, and the secondary biogenic gas generation simulation experiment with different coal rank coals been degraded by methanogens which existed in low, middle, and high rank coals, will be researched in this project. The characteristics and generation process of secondary biogenic gas will be also obtained. By using the technologies of Gas Chromatogram and Elemental Analysis added Mass Spectrometry, the yield of secondary biogenic gas generation and carbon conversion rate can be quantitatively got. The diversity of microbe living in low, middle, and high rank coals and the distributing characteristics of dominant bacteria will be revealed according to high-throughput sequencing technology. We will also discuss the change in composition, molecular structure, and functional group content of coal samples being degraded before and after, and further reveal the mechanism of secondary biogenic gas generation. Based on the analysis of test and experiment results, the relation of secondary biogenic gas yield and the parameters of dominant methanogen genus, maturity, and maceral contain can be built. Finally, the best scheme of maximizing hydrocarbon generation between methanogens and coals will be presented. Results will provide a theory basic for biogasification and biological mining in coals.

自从美国圣胡安盆地发现次生生物煤层气以来，次生生物气对煤层气的资源贡献越来越引起人们的关注，但对于不同变质程度的煤储层中微生物多样性、差异煤阶次生生物气生成演化特征与生烃机制研究较少。通过系统采样，开展产甲烷菌群驯化、富集培养及不同产甲烷菌降解差异煤阶煤岩生烃模拟实验，表征次生生物气生成演化特征；运用气相色谱技术、元素分析与质谱联用技术，定量生物甲烷生成量与碳转化率；借助高通量测序技术对代表低、中、高变质程度的煤岩微生物多样性进行研究，确定优势产甲烷菌分布规律；通过FTIR与RS等技术测试，探讨微生物降解前后煤的物质组成、分子结构和官能团含量变化规律，揭示次生生物气生成演化机制；综合上述测试及实验结果，分析次生生物气的生成潜力与产甲烷菌优势种属、煤岩变质程度、显微组分含量之间关系，确定一种产甲烷菌群（本源或外源的）作用既定煤阶煤岩生烃最大化的组合方案，为生物气化和生物采煤提供理论依据。

开展差异煤阶次生生物气生成演化特征及微生物作用机制研究对增加煤层含气饱和度、提高单井产能具有重要意义。通过为期123天的室内微生物降解煤有机质生烃模拟实验，阐明生物甲烷生成潜力，分析煤层产出水与富集培养液中微生物多样性，探讨影响生物甲烷生成潜力的主控因素，研究构造演化对煤层气的控制作用，揭示微生物降解煤有机质生烃演化机理。研究发现：煤岩样品（LLM03）的最大生物甲烷产率为98.5µmol/g。甲烷叶菌属（Methanolobus）和甲烷杆菌属（Methanobacterium）是芦岭矿煤层产出水中的优势古菌菌种类型。镜质组含量与煤岩生物甲烷转化产量之间具有负相关关系，挥发份与生物甲烷生成潜力之间具有正相关关系。对于烟煤和无烟煤样品来说，镜质组含量越高，生物甲烷生成量越低；同时，挥发份含量越高，越利于生物甲烷的转化。挥发份含量高低是影响微生物降解煤岩生成生物气的最重要的内在地质因素。煤层产出水中硫酸盐还原菌的存在会阻碍生物甲烷的生成潜力。构造演化过程控制不同成因类型煤层气的富集与成藏，经历最大埋深小于6000 feet且有机质成熟度小于0.5%的煤层以富集生物成因气为主。厌氧微生物会优先降解脂族结构，芳香结构也可以降解。微生物作用有利于改善煤岩大孔孔容，微米级优势孔隙与平均孔径会增大。