深部煤层气储层微观结构及储渗机理

Microstructure and reserve-seepage mechanism of deep coalbed methane reservoir

采用扫描电镜观察了北京大安山煤矿和阜新五龙矿煤层气储层样本的微观结构,分析了煤层孔隙和裂隙的类型、大小、连通等结构特征及结构与煤层气储集和渗流间的关系,运用图像处理技术,基于扫描图片提取并分析了煤层孔隙度.结果表明:北京大安山煤矿煤层气储层样本是典型的低孔隙度、低渗透性储层,以微孔隙、极微孔隙、微裂隙、极微裂隙为主;阜新五龙矿煤层气储层样本是典型的高孔隙度、高渗透性储层,孔隙类型多样,存在大孔、大裂隙,孔隙之间和孔、裂隙间连通性好,十分利于煤层气的渗流和产出;煤层中孔隙较多、孔径适中的结构有利于煤层气的吸附储集,煤层中大孔和裂隙有利于煤层气的游离储集,煤层中裂隙延伸长而宽,孔隙间连通,孔、裂隙相沟通的结构有利于煤层气的渗流和运移.

Based on observation results of microstructure of the Beijing Da Anshan Coal Mine and Fuxin Wu long Coal Mine CBM Reservoir samples with SEM method, the characteristics of coal seam such as pores and cracks type, size, connectivity and relation between CBM Reserve-seepage and microstructure of coal seam were analyzed. Coal seam porosity based on the scanned images by Image Processing Method were extracted and analyzed. The results shows that the methane reservoir samples of Beijing Da Anshan coal mine are typical low porosity and low permeability reservoir mainly with micro-pores, minimal-pores, micro-cracks, and minimal-cracks. In contract with this, the methane reservoir samples of Fuxin Wulong mine are typical of high porosity and high permeability reservoirs. And they have diverse type pores, large pores and cracks and good connectivity presence. All of these are very conducive to seepage and output of CBM. This paper assumes that more types and moderate size pores structure of the CBM reservoir are in favor of coalbed methane adsorption reservoir, and large pores and cracks are in favor of free coalbed methane reservoir. In addition, extended long and wide cracks and good connectivity between pores or between pores and cracks are in favor of CBM seepage and migration.