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Accuratecoal-bed methane （CBM） resource estimation becomes significantfor CBM extraction through ground CBM wells and underground coal mines,and adsorbed gas accounts for more than 80% of the total CBM in placeresource in subsurface coal seams. However, the CBM resource estimationpresents many challenges, especially the inappropriate adsorbed gasestimation method and the oversimplified adsorption thermodynamicsdescription. This work tackles both issues by utilizing a dual-siteLangmuir model to describe supercritical methane adsorption behaviorin anthracite and analyze the corresponding thermodynamic characteristics.The proposed model not only accurately describes measured adsorptionisotherms under elevated pressures （up to 17 MPa） and temperatures（up to 352.55 K） and interprets all observed adsorption phenomena,but also can extrapolate the adsorbed gas content and the total gascontent at subsurface conditions beyond test conditions. The estimateddensity of the adsorbed methane is found to be temperature and pressuredependent, which is higher than the gas density but lower than theliquid methane density. The isosteric enthalpy of adsorption for methanein coal shows adsorption uptake dependence and temperature dependencebehavior. Using the classic simplified Clausius–Clapeyron equationoverestimates the isosteric enthalpy of adsorption, which cannot revealthe associated temperature dependence behavior. Furthermore, the proposedmethod is applied for estimating deep CBM in place resource and understandingcoal and gas outburst prediction technology by using the temperaturemeasurement approach.
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