沁水盆地南部高煤级煤储层孔隙分形特征

以沁水盆地南部的20个高煤级煤样品的压汞实验和煤岩煤质分析的结果为依据,探讨了孔隙分形维数的计算方法,分析了盆地南部地区高煤级煤孔隙分形特征。研究表明,高煤级煤孔隙分形无标度区为50nm~100μm,孔隙分维数在2.94~3.21,孔隙分维数与煤变质程度、孔隙度、大孔含量、体积中值孔径呈负相关关系,与中孔含量、吸附孔含量、退汞效率、灰分产率呈正相关关系,而固定碳含量、镜质组质量分数、挥发份产率、兰氏体积则以孔隙分维数3.05为拐点呈双U形或倒双U形变化。孔隙分维数可以作为反映高煤级煤储层吸附能力和解吸能力的一个重要参数,并依据孔隙分维数划分出该区富气易解吸区、富气难解吸区及含气解吸区。

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.