Using molecular simulation methods,the variation patterns of the pore structure of asphalt under three different conditions were explored:constant temperature and variable pressure(T-Ps),constant pressure and variable temperature(Ts-P),and coupling of temperature-pressure(Ts-Ps).The adsorption and diffusion mechanisms of methane in asphalt were also investigated.It was found that both temperature and pressure significantly affect the pore structure of asphalt.Methane adsorption in asphalt is promoted by increased pressure and pore structure,whereas methane adsorption is inhibited by higher temperatures.Under temperature-pressure coupling conditions,a trend of initially increasing and then decreasing methane adsorption in asphalt was observed.This suggests that at lower temperatures,methane adsorption in asphalt increases with increasing pressure,whereas at higher pressures,methane adsorption in asphalt is hindered by temperature.Additionally,it was demonstrated that the diffusion coefficient of methane under ultra-deep conditions is primarily influenced by temperature.Overall,the study revealed the evolution of pore structure in asphalt under ultra-deep conditions and elucidated the occurrence mechanism of methane in asphalt,providing theoretical support and valuable guidance for understanding the preservation mechanism of hydrocarbons in ultra-deep reservoirs.
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