Microscopic characteristics of the methane occurrence state in coal

Abstract

The regulation of methane occurrence is critical for gas control. Through liquid nitrogen adsorption, isothermal adsorption/desorption of methane and electrical experiments with undeformed and deformed coal, this paper studies the microscopic characteristics of methane occurrence. The results show: the median-pore-dominant deformed coal has less specific surface area and pore volume than the undeformed coal, which has mainly micropores and small pores; the deformed coal has greater methane absorption ability than the undeformed coal, and the negative influence of temperature on the former is more notable; the resistivity of deformed coal is three to seven times that of undeformed coal, and when adsorbing the resistivity of both coals decreases before being stable, whereas their dielectric constant rises first, then slightly declines. The results of the three experiments are in good accordance. The research is basic for coalbed gas and may provide a new thought for gas control.