Experimental Study On The Adsorption And Desorption Properties Of Shale In Different Particle Sizes

Social progress has a strong dependence on energy.Increasing energy consumption year by year will induce problems such as energy shortage and excessive pollution.The current status of"oil shortage and gas shortage"makes China's crude oil and natural gas highly dependent on foreign countries.To ensure the long-term and stable supply of energy,shale gas as an unconventional new energy source can alleviate the shortage of conventional energy sources to a certain extent.However,the study of shale gas in China is still in its infancy,and many basic studies are not deep enough.The development of shale gas urgently needs to clarify its basic physical characteristics-adsorption and desorption characteristics.The paper mainly discusses the relationship between shale adsorption and desorption performance at different particle sizes from the perspective of shale gas reserves.Analyze the relationship between adsorption and desorption characteristics and kinetics,use the appropriate adsorption type to fit the relevant detection physical quantity of isothermal adsorption,and then use the relevant theory to analyze the isothermal adsorption of shale.The experiment selected the shale of Longmaxi Formation in Changning County,Sichuan Province as the sample for this experiment.Using the control variable method to carry out adsorption and desorption experiments on shale of different particle sizes,the analysis of experimental data can objectively and accurately reflect the influence of particle size on shale adsorption and desorption.This basic research provides recommendations for shale gas from reserves prediction to exploitation and utilization,on this basis,a comprehensive evaluation of the shale gas is made.And got the following conclusion:(1)Collected and prepared 9 sets of granular pages with cylindrical block,centimeter-level particles,4?2 mesh,8?4 mesh,30?8 mesh,60?30 mesh,120?60 mesh,200?120 mesh,400?200 mesh for rock samples,the volumetric method samples were used for isothermal adsorption experiments at 30?.It is found that the effect of particle size on shale adsorption is a weakly related influencing factor with respect to temperature and pressure.Among the 9 sets of particle size,the overall shale particle size and adsorption capacity are negatively correlated.(2)The fit of the gas adsorption Langmuir model to the shale adsorption of CO₂ is high,indicating that the shale adsorption of CO₂ is consistent with the adsorption of single molecules.As the particle size decreases,the limit adsorption capacity tends to increase.(3)Select 5 groups of cylindrical block,4?2 mesh,30?8 mesh,60?30mesh,200?120 mesh particle size for 30?isothermal pressure desorption experiment,and found that the effect of particle size on desorption amount is only reflected in time In effect.The desorption time of columnar shale is obviously higher than that of other granular and powder samples.After completing the 30?isothermal constant pressure desorption experiment,the temperature desorption experiment was carried out on the 5 groups of particle sizes,and it was found that the difference in particle size did not change the desorption increment and desorption time.(4)The curve of adsorption and desorption with time shows that as the particle size decreases,the adsorption rate and desorption rate of shale adsorbed gas become larger.From the macroscopic view,the time required for the shale sample to reach the adsorption and desorption equilibrium becomes shorter.From the microscopic view,the sample with a smaller particle size often has a more complicated pore structure,which makes the adsorption-desorption reaction at the gas-solid interface more active.(5)The shale adsorption curve of N₂ and CO₂ gas is verified in the low pressure section,and the adsorption capacity increases with the pressure.Under the same experimental conditions,the relationship between the adsorption capacity of each gas is:N₂<CO₂.(6)In the experiment of the relationship between volumetric pressure and shale permeability,it is concluded that shale has the characteristics of low porosity and low permeability,the change of porosity with the rock sample pressure state is gradual and there is no jumpy change.