The characteristics of nanopores in high rank coal reservoir based on FE-SEM and low temperature nitrogen adsorption

摘要

Based on experimental techniques including argon ion polishing-field emission scanning electron microscopy(FE-SEM)and low temperature nitrogen adsorption, the characteristics of nanopores in high rank coal reservoir in Xinjing Coal Mine of Yangquan in Shanxi province were analyzed.The results show that the average pore surface area, porosity and pore diameter is 0.llm2/g, 0.000683cm3/g and39.31nm, respectively.The peak value of the pore size distribution are mainly concentrated under 100nm.A variety types of pores including phyteral cell residual pore, matrix pore, clay mineral pore,quartz intragranular pore, pore between components and micro-fractures were identified, Among these pores, the phyteral cell residual pore holds an absolute development advantage and correspond to the main aperture diameter (＜l00nm).The micro-fractures is not developed well.Nanopores has significant fractal characteristics and strong microscopic heterogeneity.In high-rank coal reservoirs, nanopores develop well while primary micro-fractures do not.Such a feature indicates high-rank coal reservoirs have stronger adsorption capacity, higher methane content but poor penetration ability.In addition, the percolation ability of reservoirs is various as a result of the strong anisotropy and heterogeneity.Given the above two reasons, we propose that high-rank coal reservoirs have large CBM resource potentiality but remarkable problems in production capacity.