Grand Canonical Monte Carlo Simulation Of CH₄ Adsorption In Kerogen

Shale gas is one of unconventional gas resources, it is natural gas which extract from shale. The state of aggregation of shale gas in gas reservoir has diversity, the mean form are adsorbed gas and free gas, and a small amount of dissolved gas. Adsorbed gas is adsorbed on the particulate organic matter, clay mineral particles and rock pore’s surface. Organic matter content of shale gas reservoir is one of the key factors which affects the adsorption capacity of shale. Kerogen is the main form of organic matter content in shale. Therefore, studying shale gas adsorption in kerogen is of great significance for studying the form of shale gas in reservoir, and provides some theoretical guidance to the resources predictions.In this paper, Grand canonical ensemble Monte Carlo（GCMC） simulation is adopted to study the adsorption capacity of methane（CH₄） single component adsorption and methane/Carbon dioxide（CH₄/CO₂） binary adsorption in kerogen. The influence of gas partial pressure, kerogen types on adsorption heat and adsorption amount is investigated.Methane single component adsorption, the simulation results show that:（1） Adsorption heat and adsorption amount of CH₄ in 3 different kerogen are the same, C128 > C406 > C415;（2） The change of pressure has little effect on adsorption heat of CH₄;（3） When pressure is low, adsorption amount of CH₄ increases rapidlly with increasing pressure; then adsorption amount increases slowy; when thr pressure is relatively high, the reason of adsorption amount of CH₄ increment is the density of CH₄ increases with increasing pressure.Methane/Carbon dioxide binary adsorption, the simulation results show that:（1） Adsorption heat and adsorption amount of CO₂ in 3 different kerogen are bigger than that of CH₄;（2） Adsorption heat and adsorption amount of CH₄ and CO₂ in 3 different kerogen are the same, C128 > C406 > C415;（3） The partial pressure of CH₄（or CO₂） has little effect on adsorption heat of CH₄（or CO₂）;（4） The adsorption amount difference between CH₄ and CO₂ gradually increases with increasing of CO₂ partial pressure.