Amount of adsorbed gas in deep coal reservoir based on adsorption potential theory

In order to reveal the deep coal reservoir adsorption characteristics of coal and the quantitative characteriza- tion on the amount of adsorbed gas of coalbed methane,this paper studied the coal samples of carboniferous-permian in eastern Ordos Basin and analyzed the methane isothermal adsorption experiments of high temperatures and pressures of coal samples. An interpretation of the adsorption characteristics was made under high temperatures and pressures from the geological factors including coal rank,temperature and pressure. The curves of coal adsorption characteristic and the prediction model of amount of adsorbed gas with different coal ranks were established based on the adsorption po- tential theory. Meanwhile,a case study on the amount of adsorbed gas of the No. 8 +9 coal seam in Linxing area was analyzed based on this model. The results show that the adsorption characteristics of deep coal reservoir are compre- hensively influenced by temperature,pressure and coal rank. When the coal rank is between 0. 77% and 2. 18% , which is from gas coal to poor coal,the coal rank and pressure show a positive effect on adsorption ability,but tempera- ture has a negative effect. In addition,the negative effect is more significant with the pressure increases. Different coal ranks have different curves of coal adsorption characteristic. The higher of coal rank,the slower of rate at which the ad- sorption potential decreases as the adsorption space increases. The calculation of the amount of absolute adsorbed is between 19. 6 cm3 / g and 31. 1 cm3 / g,and the gas saturation is between 37. 8% and 78. 8% in the study area.