Molecular Dynamics Simulation Of Adsorption And Replacement Of CH₄,CO₂,H₂O In Nanocone

In the face of severe situation that the conventional oil and gas resource cannot meet the world,s energy need gradually,coal bed gas and shale gas are gradually taken care by people as a new of green energy.Coal bed gas and shale gas are widely distributed,rich in reserves,low in pollution and great in exploitation potential.The development of coal bed gas and shale gas are significant in alleviating the energy to be short and ameliorate the form using energy in China.With the development of simulation technology and computer technology,the scale of researched materials has been extended from macroscopic to microscopic angles,from microscopic to nano-scale angles,and the application of molecular simulation technology has important great practical significance in revealing and predicting the nature of CH₄ adsorption,CO₂ and H₂O force fracturing and CO₂ replacement of CH₄.In conclusion,the sorption of CH₄?CO₂ and H₂O in the nanocone and on the nanocone wall were investigated at the molecular level using molecular dynamics.In this study,the adsorption of CH₄ and CO₂ was compared in the aspects of energy,configuration,structure,capacity and etc.The adsorption energy is in the order of CO₂<CH₄<H₂O which implies that CO₂ adsorbs in the nanocone more easily than CH₄ and H₂O and can be a good candidate in displacing CH₄.The equilibrium distance between centroid of CH₄,CO₂ versus H₂O and nanocone tip are 2.25 nm,2.10nm,2.27nm.The equilibrium distance between CH₄?CO₂ and H₂O?and the nanocone wall is in order of H₂O>CH₄>CO₂.The lower the adsorption energy is,the easier the molecule adsorbs in nanocone,which indicates that CO₂ is the best candidate in displacing CH₄.The final study shows that with the increase of temperature,the adsorption quantitative change of nanocone to CH₄ is smaller,and the greater the pressure,the more obvious the change trend of nanocone adsorption with temperature.By comparing the adsorption phase and the bulk phase density is found at the same temperature and pressure,the adsorption density is greater than the bulk density,which indicates that nanocone store more methane.By comparing the displacement efficiency of the restricted methane in the replacement nanocone,it was concluded that carbon dioxide is greater than water and natural desorption.It is also concluded that when the initial pressure of CO₂ is 1/2 of the pressure of methane in the nanocone,the displacement efficiency is the best,so almost all CH₄ in the nanocone is replaced.For H₂O,it can block the replacement of CH₄,which is not conducive to the recovery of CH₄.