The Study On Increasing Production Law Of Coal Seam Nitrogen Injection

Most coal bed methane wells exploited in China are in reservoirs with low pressure,low permeability,low saturation and strong heterogeneity.It is necessary to improve production through stimulation treatments.In the process of coal bed nitrogen injection fracturing,nitrogen has produced additional stimulation effect on the replacement of coal bed methane in addition to the stimulation effect of fracturing,In order to promote the understanding of the laws of nitrogen injection in coal bed and provide the best production,this paper takes 15#coal in Qiyuan Area as research object.The purpose of this research is characterizing the adsorption performance of N₂ and CH₄by isothermal adsorption experiment,and the micro-competition process of coal adsorption gas by molecular dynamics simulation method.The results show that the adsorption capacity of CH₄ and N₂ increases with pressure by Langmuir’s adsorption law at a specific temperature.The adsorption capacity of coal to N₂ is weaker than that of CH₄.When the two gases mixed,the competition adsorption occurs between N₂ and CH₄.At the same partial pressure,the saturated adsorption capacity of mixed gas of CH₄ is lower than that in the single component state.The adsorption energy of CH₄ in the gas decreases with adsorption site shifting to the right.In other words,the decreasing of adsorption capacity.In the adsorption process,the adsorption speed of CH₄ is fast at first and slows down later,which is influenced by the concentration of free phase,indicating that the adsorption competition situation of gas molecules changes gradually as the concentration change.