With the example of Shanxi Formation high rank coal and shale samples, the pore structure characteristics of the sample was studied through the hypothermia nitrogen adsorption experiments.At the same time, the fractal dimension of the sample based was calculated on the Frenkel-Halsey-Hill equation and carry out the comparative study of pore fractal characteristics between the coal seam and shale.The results showed that: shale samples are mainly distributed in micropores, also contain a certain amount of transition-pores, the main reservoir space is provided by the micropores and transition pores, transition pores are the main pores in high rank coal samples, the reservoir space is provided by transition pores;In the test range, the specific surface area of high rank coal is much larger than that of shale samples;The pore morphology of shale is mainly parallel-plate pores and fractured pores, and some flask pores.The main pore shape of high rank coal is closed pore, which indicates that the shale reservoirs have the powerful permeability in microcosm, and maybe it is one of the reasons that the proportion of free gas in the shale is higher than the that in coal seams.The shale and high rank coal are both with significant fractal characteristics, the fractal dimension of the sample is larger than that of the high rank coal, which indicates that the spatial structure of shale porosity is more complex and heterogeneous than that of the high rank coal.At the same time, both of the shale and high rank coal have the dual fractal feature, the fractal dimension of shale seepage pore is smaller than that of adsorption pore, which indicates that the pore structure of shale adsorption pore is more complex.Compared with the shale, the fractal dimension of high rank coal seepage pore and adsorption is smaller, the pore size of high rank coal is mainly seepage pore, which is beneficial to the CBM gas production reaches the peak quickly, while the pore size of the shale is mainly micropore and seepage pore, which have the higher adsorbed gas content, and the pore structure of seepage pore is mainly parallel-plate pore, which is simpler than that of micropore.%以山西组高煤级煤与页岩样品为例,通过低温氮气吸附实验研究了样品的孔隙结构特征,并基于FHH分形模型计算了样品的分维值,对页岩与煤层的孔隙分形特征进行了对比研究.结果表明:页岩样品以微孔为主,同时含有一定量的过渡孔,主要的储集空间由微孔和过渡孔提供.高煤级煤样品以过渡孔为主,主要的储集空间由过渡孔提供.在测试孔径范围内,页岩样品的比表面积远大于高煤级煤.页岩的孔隙形态上以四周开放的平行板孔和裂缝型孔为主,具有部分细颈瓶孔,高煤级煤的孔隙形态以封闭型孔为主,反映页岩储层微观渗流能力更强,可能是页岩中游离气比例高于煤层的原因之一.页岩与高煤级煤均具有显著的分形特征,页岩样品分维值高于高煤级煤,说明页岩孔隙的空间结构比高煤级煤更为复杂,非均质性更强;同时二者均具有双重分形特征,页岩渗流孔分维值低于吸附孔,反映页岩吸附孔孔隙结构更为复杂.与页岩相比,高煤级煤渗流孔和吸附孔的分维值均小于页岩,孔径分布集中于过渡孔,有利于煤层气快速到达产气高峰;而页岩孔径分布则集中于微孔和过渡孔,吸附气含量更高,并且过渡孔的孔隙结构以平行板孔为主,孔隙结构特征较微孔简单.
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