Study on Adsorption Characteristics of CH₄ in Deep Coal Reservoir Based on Ono-Kondo Lattice Model

To more accurately study the adsorption characteristics of coalbed methane in deep coal reservoirs, and to understand the effects of different factors such as temperature, pressure and water on adsorption of CH₄ in coal seams, we accurately described the isothermal adsorption curves of CH₄ in four different rank coals under different temperature and pressure conditions, before and after different fluids. In this paper, we adopted simplified Ono-Kondo lattice model fitting method. The results show that pressure has a positive effect on adsorption of CH₄, and temperature has a negative effect on adsorption of CH₄. The higher the pressure is, the greater the influence of adsorption on temperature. Moisture will reduce the maximum adsorption capacity of coal to CH₄, which is not conducive to adsorption of CH₄. Supercritical CO₂ extraction can increase the micropore surface area and pore volume of coal to increase the maximum adsorption capacity of CH₄ in coal seam. The maximum adsorption amount shows a “U” type relationship with the change of coal rank.