Molecular Simulation Of Shale Gases Adsorption In Organic Nanopores Of Shale

With the decrease of quality conventional resources,people have turned their attention to unconventional oil and gas resources.Shale gas is a type of unconventional gas that is harder to exploit because of the tight of the shale.How to develop shale gas reservoir more efficiently and economically is a topic of common concern.Shale have small pore size and large specific surface area.The gas of adsorbate state have a large proportion.In the investigation of shale gas resource evaluation,diffusion and seepage all need to consider the influence of the adsorbate gas.Laboratory measurements can investigate the isothermal of CH4 at different temperatures on shale powder or cutting samples,may not capable of providing macroscopic information.Scanning electron microscope although powerful,may not provide us with an understanding of the underlying mechanisms of gas storage.Besides the experiment and theory,molecular simulation is another research method which are attractive supplements to the macroscopic isothermal measured experiments,as such simulations can visualize the adsorption status in nanopores directly and provide more details that is not possible to obtain by laboratory measurements alone.In the current work,molecular simulations have been carried out using a grand canonical monte-carlo method and molecular dynamics method to study the shale gas adsorption in graphene slit holes,in which the effect of composition of gases,temperature,pressure,aperture on the isothermal are observed.Moreover,shale gas adsorption in kerogen is studied with the consideration of the influence of kerogen type,constitute of gases,and the adsorption selectivity of C2H6 over CH4.The competitive adsorption of CH4 and CO2 in the carbon-based slit pores of a given width is also investigated.Burial depth,composition and other factors were studied.The density distribution of CH4,CO2 in the pore and the adsorption selectivity of CO2 over CH4 are also analyzed.Among the works mentioned above,some specific conclusions are listed as following:(1)with the increase of the pressure,the excess sorption of the gas increases firstly and then decreases.The higher the temperature,the greater the pressure at which the excess adsorption reaches the maximum value.Heavier component has stronger adsorption capacity.With the increase of pressure,the adsorption of C2H6 in the smaller nanopores was increased and then decreased.The gas adsorption and pore size are nonlinear;(2)?-D type kerogen model has a larger adsorption capacity compared with ?-C.The selectivity of kerogen for C2H6 relative to CH4 increases with increasing of pressure.The interaction between the sulfur atoms and the gas molecules is strongest.The interaction distance between hydrogen and gas molecules is minimal.(3)In the case of ratio of CH4:CO2=4:l,the sorption of methane adsorption increased with the increase of buried depth,but the sorption of carbon dioxide adsorption did not change much.In the case of ratio of CH4:CO2=1:1,there is a large proportion of CO2 in the pore wall,but the amount of CH4 in the center of the pore is slightly larger than that of CO2.The CO2 of adsorbate state is parallel to the pore surface.The higher CO2 ratio,the larger selectivity of graphene for CO2 relative to CH4.