Molecular Simulation Studies Of Shale Gas Adsorption Behavior In Reservoir

Shale gas,as a potential for unconventional energy sources,its main component is methane,and its occurrence in different ways with conventional natural gas,there was a small amount shale gas dissolved in organic matter or structure of water,most of shale gas stay in the vug and fracture of the shale with free state and adsorbed on the surface of organic matter with adsorption state.In this paper,molecular simulations were used to investigate the adsorption behavior of CH₄/CO₂ in shale gas reservoir and the effect on CH₄/CO₂ adsorption behavior in presense of water.Based the simulation,the main content and contribution are summarized as follows:?1?The adsorption behavior and self-diffusion mechanisms of CH₄/CO₂ in kerogen?4layers graphite?slit pore of sizes from 0.72 nm to 4.0 nm have been studied by molecular simulations,The temperature plays a major role on the methane adsorption at low pressures,when the high pressure,the pressure effect is more pronounced.The CH₄/CO₂ was dsorption state when the graphite slit pores less than 2.0 mm and showing both adsorption state and free state when the graphite slit pores bigger than 3.0 mm.there was a negative effect on CH₄/CO₂adsorption behavior in presense of water.The more water the less CH₄/CO₂ adsorption.?2?In this work,molecular simulations have been used to research realistic 3-D molecular model of kerogen including carbon?C?,hydrogen?H?,oxygen?O?,nitrogen?N?and sulfur?S?atoms using grand canonical Monte Carlo?GCMC?and molecular dynamics algorithm to evaluate the CH₄/CO₂ adsorption behavior and the adsorption selectivity of CO₂,analyzed the effect of water,and systematically elucidated the role of Coulomb and van der Waals interactions in CH₄/CO₂adsorption.The RDFs show that the N,S atoms?N,S-containing functional groups?have same effect on CH₄/CO₂ adsorption within kerogen samples.The preadsorbed water has a negative effect on the adsorption of CO₂/CH₄ duo to its larger adsorption energy than CH₄/CO₂.?3?The idealized montmorillonite?MMT?structure have been built to model clay minerals,molecular simulations have been conducted to study gas adsorption in clay minerals.The resilt shows that the charge have less effect on CH₄ adsorption and have lager effect on CO₂ adsorption.The preadsorbed water can form a water film to prevent CO₂/CH₄ adsorption.