Study on pore structure and fractal characteristics of shale from coal measures of Longtan Formation in western Guizhou

In order to study the micro-pore structure characteristics of coal shale,taking the shale from coal measures of Longtan Formation in western Guizhou as the research object,based on SEM and low temperature nitrogen adsorption test,the pore characteristics are characterized qualitatively and quantitatively,meanwhile,using fractal theory analyze its fractal characteristics and the factors influencing the pore structure.The results showed that under scanning electron microscope,intergranular pores,intragranular pores,microfractures and organic pores were observed,there are a lot of microfractures,providing a channel for hydrocarbon gas migration,and only a few organic pores;the nitrogen adsorption isotherm of shale is similar to that of Type Ⅳ,the curves are all inverted S type,reflecting that it is mainly mesoporous,forming hysteresis loop in high specific pressure zone (0.45