Full-size pore structure characterization of deep-buried coals and its impact on methane adsorption capacity: A case study of the Shihezi Formation coals from the Panji Deep Area in Huainan Coalfield, Southern North China

Abstract

Abstract The characteristics and influence on methane adsorption capacity of the pore structure of coals was investigated through an approach that integrates mercury intrusion porosimetry, low pressure N2/CO2 adsorption, and field emission scanning electron microscopy. Shihezi Formation coal samples from the Panji Deep Area in Huainan Coalfield in Southern North China were adopted as the study subjects. The fractal features of heterogeneous coal pore structures were quantified on the basis of N2 adsorption isotherms by using the Frenkel−Halesy−Hill (FHH) model. Pore structure and morphology characterizations confirm that Shihezi Formation coals developed with multiple pore types and heterogeneous pore structures, and the slit-shaped and ink-bottle-shaped pores are mainly distributed at the pore size interval of 3.3–10\u202fnm. Our coal samples present uni-modal and multi-modal pore size distributions, wherein multiple peaks are concentrated in the intervals of 0.45–0.55\u202fnm and 2–20\u202fμm. The major volumes from mesopores (2\u202fnm\u202f \u202f50\u202fnm) occur in the full-scale pore size distributions, revealing Shihezi Formation coals are mesopores and macropores rich. Micropores (pore diameter