生物甲烷代谢对煤孔隙结构的影响

Impact of Biogenic Methane Metabolism on Pore Structure of Coals

微生物代谢把煤转化为甲烷为主的气体,不但增加煤层气资源量,还能实现煤储层的生物增透。选择3种煤阶煤样进行模拟生物甲烷生成实验,通过压汞法分别测试代谢前后煤的孔隙结构,并通过X-射线衍射和FTIR测试代谢前后煤大分子结构。结果表明:1生物甲烷代谢后煤样大孔孔容及所占比率显著增加,小孔和微孔孔容有所减少,总孔容、平均孔径和孔隙度也相应增加,而孔比表面积有一定程度降低;2微生物作用后煤样的开放型孔增加,孔隙连通性增强;3生物甲烷代谢改变煤孔隙结构是通过生物酶作用于其大分子结构,使官能团和侧链脱落,苯环打开,氧含量增加,煤的晶化程度降低。微生物把煤转化为生物甲烷的同时,改善了煤的孔隙结构且降低了比表面积,有利于煤层气的解吸和运移产出,对煤层气开发有重要潜在意义。

Microbial metabolism is capable of converting coals into gaseous fuels mainly consisting of methane,which will increase the resources of coalbed methane(CBM)as well as enhance the permeability of coal reservoirs microbiologically.Three coal samples with different-rank were selected to experimentally simulate the generation process of biogenic methane,and the pore structures were tested by the adoption of mercury intrusion method and further the macro-molecular structures were determined in use of X-ray diffraction and FTIR before and after metabolism.The results show that:(1)The volume of macro-pores and their proportion increased significantly due to the impact of methanogenic metabolism,while the volumes of small pores and micropores saw a decrease;pore volume,average pore diameter and porosity had a relative increase in contrast to the reduction of pore specific surface area;(2)More open pores were generated after metabolism,thus leading to the enhancement of pore connectivity;(3)The enzyme,as a cause of the falling of functional groups and side chains and the opening of aromatic rings on the macro-molecular structures of coal,played a vital role in the rising content of oxygen and the reduction of crystallization degree of coal.In the meantime of converting coals into methane,microbes can improve the pore structures of coals and reduce the specific surface area,which is beneficial to desorption,migration and production of CBM and of great potential significance for CBM development.