利用FE-SEM、HIP、N2吸附实验表征生物气化煤系有机岩储层微观孔隙结构演化

Micropore Structure Evolution of Organic Matters in Coal Measures due to Bioconversion Using FE-SEM, HIP and N2 Adsorption Experiments

微生物降解前后的煤系有机岩(煤岩和泥页岩)储层微观孔隙结构的变化对生物成气和成藏过程具有重要的意义.利用场发射扫描电子显微镜、高压压汞仪、孔比表面积孔隙度分析仪以及分形维数理论对厌氧微生物降解前后的煤系有机岩样品储层孔隙结构演化进行分析,根据孔隙结构特征并结合微生物生态学特征,将生物气化煤系有机岩的孔隙结构类型分为3类,即孔隙直径大于5μm的微米孔,孔隙直径介于5μm^100 nm的微纳孔,以及孔隙直径小于100 nm大于2 nm的纳米孔.微生物作用后的煤岩与泥页岩的微米孔孔容增加,微纳孔和纳米孔孔容减小,孔隙比表面积降低,平均孔隙直径增大.分形维数对比结果表明受微生物作用的煤岩与泥页岩样品的面分形维数(D1)和孔隙结构分形维数(D2)均降低,微生物作用使得有机岩孔隙表面变的光滑,孔隙结构变得简单,有利于游离气的运移和富集.

Micropore structure characterization of organic matters in the coal measures due to bioconversion is of great significance in understanding reservoir reformation by microorganism and revealing the storage and enrichment mechanism of biogenic gas in the coal measures.Pore structure evolution of organic matters in the coal measures degraded by microbe was analyzed using field emission scanning electron microscopy(FE-SEM),high-pressure mercury intrusion porosimetry(MIP),low-pressure N2 gas adsorption pycnometry and fractal dimension FHH theory in this study.Considering the measuring range of pore size distribution(PSD)and combining the characteristics of microbial ecology,the pore structure type of coal and shale in coal measures is divided into three types.They are micropore(PSD>5μm),micro-nanopore(5μm-100 nm),and nanopore(2-100 nm).The PSD and micropore pore volume(PV)of coal and shale samples increase,and the specific surface area(SSA)and micro-nanopore and nanopore PV decrease after bioconversion.The surface fractal diameter(D1)and pore structure fractal diameter(D2)of coal and shale samples decrease after bioconversion,showing that the inner surface of pore becomes smooth and pore structure gets simple due to microbial action.The reformation of pore structure due to bioconversion is benefitial to the migration and enrichment of free gas in the coal measures.