生物甲烷代谢与煤结构全程演变的耦合机理研究

Biogenic methane is a product of coupling reaction between microbial metabolism and evolution of coal structure, and our recent researches indicate that pore structures of coal reservoirs and affinity to methane will be significantly improved while gaseous products (mainly methane) are being produced in the metabolism process. The investigation on variation patterns and response mechanisms of coal structures varying with biogenic methane metabolism not only has a theoretical importance on clarifying the generation of biogenic methane but plays a potential engineering role in achieving microbial increase of permeability and surface modification. This project intends to conduct a series of biogenic methane metabolism experiments by means of activating, identifying and cultivating the indigenous bacteria in low-rank coals, and further to investigate the controlling mechanisms of coal structure, physical and survival environment, content and type of organic substances and coal occurrence on microbial metabolism, and to precisely describe the variations of biochemistry and bio-enzyme activity and the process of organic macromolecules converting into methane. Meanwhile, this project aims to analyze the variation characteristics of each parameter on different stages of metabolism on the basis of testing the physical properties, chemistry structure and degradation products etc. By figuring out the relationships between the metabolism features, survival environment of bacteria and whole-process evolution of coal structure and the continuous production of biogenic methane,the coupling mechanisms between biogenic methane metabolism and whole-process evolution of coal structure will be finally ascertained.

生物甲烷是微生物代谢与煤结构演变相互耦合的产物，申请者近期研究表明煤层生物甲烷代谢在生成以甲烷为主气体的同时，也对煤储层的孔隙结构和亲甲烷能力有明显改善效果。探讨煤结构随生物甲烷代谢的变化规律及其响应机理，不但对阐明煤层气生物成因过程具有重要理论意义，也为形成煤储层的生物增透与表面改性技术具有潜在的工程意义。 本项目通过中低阶煤所含本源菌的激活、鉴定和培养，进行生物甲烷代谢实验，查明煤结构、存活环境、有机质含量、类型和赋存状态对菌群代谢的控制机理；精细刻画生物化学、生物酶活性变化和有机大分子向甲烷转化的过程；同时以全程跟踪测试煤的物性特征、化学结构及降解产物等为基础，分析生物甲烷代谢对煤结构各项指标的变化规律；理清菌群代谢特征、微生物存活环境变化、煤结构全程演变与生物甲烷产气之间的对应关系，最终查明生物甲烷代谢与煤结构全程演变的耦合机理。

生物甲烷是煤层气资源的重要补充，而煤结构本身又影响着生物甲烷的生成，研究生物甲烷代谢与煤结构全程演变的耦合机理对提高煤层气资源量有重要现实意义。以中低煤阶煤为主要研究对象，分析了煤岩以及煤层水特征，并进行了煤的生物甲烷代谢模拟实验，证实了厌氧发酵后的残煤仍然具有产气潜力。生物代谢过程中菌群的吸附性、迁移性观测揭示了产甲烷菌群更倾向于吸附在低煤阶煤表面，煤粒度越小吸附效果越明显；低阶煤更利于微生物的迁移，且粒度越大，越易于菌群的迁移扩散；低煤阶大粒度煤样更利于菌群随入渗水流迁移。.利用偏光显微镜、压汞、CT、等温吸附、XPS、红外光谱和X射线衍射综合分析测试，查明了生物甲烷代谢前后煤结构的变化特征。微生物作用后煤表面产生大量孔洞，裂隙连通性大大增强，煤体吸附甲烷的能力降低，更利于煤层气运移产出。煤样经微生物作用后表面芳香单元及其取代烷烃（C-C、C-H）相对含量增加，酚碳或醚碳（C-O）含量减少，羰基碳（C=O）含量增加，羧基碳（COO-）含量增加。甲基、亚甲基和芳烃含量减少，苯环被打开，煤中官能团和侧链脱落。芳香碳层面间距d002逐渐增加，延展度La和堆砌度Lc趋于减小，煤的晶化程度降低。.通过分析不同煤结构差异、抽提残煤结构变化和显微组分对生物甲烷代谢的影响，查明了煤结构差异对生物甲烷代谢的控制机理。芳构化程度低，侧链官能团和腐殖酸类活性有机质多的煤体更易被产甲烷菌群降解产气。H/C原子比、氢元素含量和脂肪烃含量与生物产气潜力正相关，芳构化程度、芳香烃含量、煤样中的微孔和微孔体积与生物产气潜力负相关，微生物产气效果好坏与平均孔径和比表面积没有明显相关性。生物甲烷代谢与煤结构全程演变的耦合机理研究，揭示了生物甲烷代谢过程，为煤层气生物工程走向工程试验提供了重要参考。