中–高煤级煤岩孔隙发育特征

Characteristics of pore development in medium–high rank coal

煤层气的吸附、解吸、扩散、运移与煤储层孔隙发育情况密切相关,煤岩孔隙特征实验研究至关重要。离心法获取煤样毛管压力资料快速简便,无毒无害,通过离心取代常规压汞来表征并划分中–高煤级煤岩孔隙结构类型,将二者实验结果进行对比,同时结合扫描电镜实验探究孔隙发育成因。结果表明:依据煤级高低可将煤岩孔隙结构划分为3类,从类型Ⅰ到类型Ⅲ,孔隙发育情况由大–中孔向微–小孔过渡,气体储运模式由吸附扩散向游离渗流过渡;离心与压汞在表征煤岩孔隙发育特征上具有一致性;不同种类的煤孔隙成因导致煤层气在各类煤储层中的储运方式存在差异。

The adsorption/desorption, diffusion, and migration of CBM are so closely related to the pore development in coals that experimental study on it is very essential. It is a fast, convenient, non-toxic and harmless way to obtain capillary pressure data of coals through centrifugation. The pore structure types in medium-high rank coal are characterized and classified through centrifugation instead of mercury injection and a comparison is made between the two methods.Meanwhile, the origin of pore development is explored with SEM experiment. The result shows: pore structure in coalscan be clas sified into three types according to the coal rank. From typeⅠto type Ⅲ, the pore development transits from macro-pores to micro-pores and the storage and transportation mode for CBM from adsorption and diffusion to free seepage. Centrifugation and mercury injection are similar in characterizing the pore development. Various kinds of pore origin in coal lead to the differences in the storage and transportation mode for CBM.