高阶煤吸附能力与其微观组分含量关系探究——以沁水盆地F区块3~#煤层为例

Relation of adsorption capacity in high-rank coal to maceral content:An example from No. 3 coal seam,F block,Qinshui Basin

煤层气是一种吸附于煤层之中的自生自储式非常规气藏,作为气藏的储集层,煤层的微观组分对其储气能力有着重要影响。为了厘清沁水盆地F区块高阶煤储气能力与其煤岩微观组分之间的关系,对同一构造带上埋深、厚度、地层压力、热演化程度相似的17个3~#煤煤岩样品进行了工业组分、微观组成、含气性、等温吸附测试,开展了各种微观组分与煤岩样品含气性及吸附性关系的研究。研究结果表明:①3~#煤的含气量与工业组分中的水分含量相关性不明显,与灰分、挥发分含量呈反比,与固定碳含量呈明显的正相关关系;②煤岩样品含气性及其对煤层气的吸附能力与镜质组含量没有明显的相关性,与惰质组含量呈正比;③高阶煤中的镜质组对甲烷吸附能力相对较弱,惰质组对甲烷吸附能力较强。结论认为:高阶煤中镜质组多以均质镜质体形式存在,凝胶化作用明显,储集空间减小,煤岩对甲烷吸附性和镜质组含量相关性不大;惰质组组分多为丝质体,保存了较多的细胞胞腔,对甲烷的吸附性能增强。

Adsorbed in coal, coalbed methane(CBM) functions as unconventional gas reservoirs with self generation and accumulation. As one reservoir, its maceral content affects severely gas storage capacity. To figure out the relation of this capacity to the content in certain high-rank coal, F block, Qinshui Basin, 17 samples from No.3 coal seam, which feature similar burial depth, thickness,formation pressure and thermal evolution degree in the same structural belt, were tested in terms of component, maceral, gas-bearing property, and isothermal adsorption. Moreover, one relationship among various macerals as well as both gas-bearing property and adsorption capacity was identified for these samples. Results show that(1) there is no obvious content correlation between gas and water, but is inversely proportional to both ash and volatile contents and apparently positive relation with fixed carbon content;(2)for the samples, not only gas-bearing property but their adsorption on CBM have subtle correlation with vitrinite content, but being proportional to inertinite content;and(3) vitrinite in high-rank coal has comparatively weak adsorption on methane while accordingly strong adsorption for inertinite. In conclusion, vitrinite mostly exists in homogeneous form with clear gelatinization and compact storage space, and there is little influence of vitrinite content on methane adsorption. On top of this, the inertinite component is dominated by fusinite, which can preserve numerous cells, thereby showing high capacity in methane adsorption.