Molecular Simulation And Experimental Study Of Shale Gas Adsorption

As an important unconventional gas resources, shale gas has abundant reserves in our country, under the condition of the energy situation is increasingly nervous, its successful development has important strategic significance.to improve the energy structure and ensure national energy security in our country. Due to its special form of existence, so that the study of shale gas adsorption mechanism is particularly important. At present, the researches on shale gas adsorption still stay at the macro level, which is the microscopic mechanism of adsorption analytical ability is limited to explain the micro mechanism of adsorption, and the relevant research about interaction mechanism of gas molecules with surface of core is very few. In addition, the shale gas exploration and development in our country is still in infancy, micro adsorption mechanism of shale gas remains to be further research. This study is supported by National Natural Science Foundation of Youth Science Foundation.Therefore, on the basis of analysis of reservoir characteristics and adsorption experiments of Ordos Basin shale gas, this paper simulates the adsorption of the pure component of methane, carbon dioxide, nitrogen and mixed component of CH4/CO2 in kerogen and illite pore by grand canonical Monte Carlo method, analyzing the effect of pressure, temperature, water cut, molar ratio of the mixture on the adsorption, and furtherly analyzes the effect of the functional group and adsorption site on the absorption of methane, researching the shale gas adsorption rule and the micro adsorption mechanism from the macroscopic and microscopic aspects.The experimental testing results show that, the mineral composition of shale reservoir of study area are mainly clay minerals and quartz, illite has the highest content in clay minerals and the pore radius distribution between 1 to 3nm; organic carbon content, temperature, water can significantly affect the adsorption of methane in shale samples, under the same conditions, methane adsorption capacity increases with the increase of organic matter content, decreases with the rising of temperature, the presence of water can reduce the adsorption quantity of shale gas, at the same condition, the adsorption quantity of carbon dioxide is the highest in the same shale samples, followed by methane, nitrogen is minimal; the Monte Carlo simulation results show that under the condition of different temperature, pressure, water cut, the adsorption rules of methane in kerogen and illite pore is consistent with the experimental testing result, when the competitive adsorption, carbon dioxide reduces the adsorption capacity of methane, the equilibrium separation coefficient of carbon dioxide is greatly influenced by pressure, and it has a peak at low pressure, then decreases with the increase of pressure until reaches a constant value; the results of density functional theory study show that the existence of the functional group with oxygen and nitrogen enhances the ability of kerogen to adsorb methane, and the methane adsorbed on kerogen is not fixed, easy to move.