Molecular Simulation Study Of Nanoporosity On Shale Gas Adsorption And Diffusion

In recent years,the progress of science and technology has brought the rapid development to the economic of our society,people are aware of the importance of energy,but the presence of a series of environmental problems aredue to the consumption of energy.As the strengthening of environmental protection and the continuous improvement of the energy structure,people are keen to find a clean,efficient,safe and reliable new energy.Having realized the underlying value of shale gas,many countries have deployed energy strategy of shale gas.Domestic and overseas experts and scholars have taken the study of shale gas resources for decades,the basic research work of shale gas is gradually completed,and has made great achievements.For a better understanding of the occurrence form of shale gas,this study based on molecular simulation software Materials Studio,using Monte Carlo method,Molecular Mechanics and Molecular Dynamics to simulate the dynamic characteristics of methane and carbon dioxide in the shale nanopore at the shale gas common burial depth 2-4km,and the grand canonical ensemble and COMPASS force field were used.The analysis of the nanopore adsorptive property of methane and carbon dioxide,the calculation of adsorption capacity and adsorption heat for different buried depth in the shale reservoir,the discussion of the relative density and self diffusion coefficient of methane in shale nanopore,and the determination the best depth range for exploitation of shale gas by using carbon dioxide replacement technology are included in this study,in order to guide the exploration of shale gas to some degree.The results indicated that the adsorptions of CH4 and CO2 were physical;The relative density of CH4 and CO2 along the normal direction of the pore inwall showed a trend of symmetric distribution and apparent adsorption stratifications appeared,what's more,the formation of the second and third aggregation level are likely to be mainly affected by stress.As a whole,the self-diffusion coefficient of CH4 and CO2 increased with the increase of buried depth,and it's consistent with the reasons for such changes of adsorption amount and adsorption heat.The mixed adsorption data showed that it's reasonable and feasible to exploit shale gas by injecting CO2 to exchange CH4.