Study on Pore Fractal Characteristics of High-rank Coal Reservoirs in Southern Qinshui Basin

Based on mercury porosimetry and coal lithotype and quality analytical results of 20 high-rank coal samples from southern Qinshui Basin,discussed pore fractal dimension computation method and analyzed fractal characteristics of pore.The study has demonstrated that,high-rank coal pore fractal scale-free range is 50nm~100μm;pore fractal dimension 2.94~3.21;negative correlation is existed between pore fractal dimension and degree of coal metamorphism,porosity,macropore ratio and volume median aperture,positive correlation with mesopore ratio,sorptive pore ratio,efficiency of mercury withdrawal and ash yield;while fixed carbon content,vitrinite mass fraction,volatile matter yield and Langmuir volume to take the pore fractal dimension 3.05 as inflexion present double U-shaped or reversed double U-shaped transformations.Pore fractal dimension can be a major parameter to reflect adsorption and desorption capacities of high-rank coal reservoir,and based on pore fractal dimension can be partitioned the reservoir into CBM-rich and easy to desorption,CBM-rich but hard to desorption and CBM-bearing desorption areas.