Dynamic Simulation Study Of Methane Desorption Under Tectonic Coal Reservoir Transformatio

A key reason for coal reservoir reforming’s poor efficiency is a failure to understand the control mechanism of pore-fissure structure evolution on methane adsorption and desorption.The theories of coal mechanics,adsorption science,diffusion kinetics,and molecular dynamics are used to guide this paper,which combines theoretical analysis,physical experiments,and molecular simulations to investigate the microscopic dynamic evolution characteristics of pore-fissure structure,the microscopic adsorption and desorption laws of methane during pore-fissure evolution,and the influence of different influencing factors on methane during coal reservoir transformation for The following are the main findings of this paper.（1）The pore structure of tectonic coal was tested using industrial analysis,elemental analysis,infrared spectroscopy,low-temperature nitrogen adsorption,and mercury-pressure tests to address the unknown control mechanism of methane adsorption and desorption during tectonic coal reservoir transformation.The results show that the main difference between tectonic coal and native coal is reflected in the pore structure,and the difference in adsorption capacity between tectonic coal and native coal is strongly correlated with porosity and pore size,while functional groups do not differ significantly.（2）To address the issue of low methane repellency during coal reservoir fracturing,the chemical structure model of W.Fuchs coal was used as the basis for analysis.Under the same injection fugacity condition,the 10nm slit pore adsorbs the most methane,the4nm slit pore adsorbs the second most methane,and the 2nm slit pore adsorbs the least,whereas the adsorption capacity is the opposite.The difference in the degree of methane desorption in the slit pores of the CO₂-CH₄ system,H₂O-CH₄ system,and N₂-CH₄system is primarily due to the different diffusion coefficients of CO₂,H₂O,and N₂,resulting in a different active degree of free methane in the pores,rather than the different adsorption capacities of CO₂,H₂O,and N₂ in the slit pores in comparison to the CH₄-N₂ system.The root mean square displacement of CH₄ in the CH₄-CO₂ system is greater,and the CH₄ molecule is more active,than in the CH₄-N₂ system.When the temperature is 298 K and the CO₂ to N₂ ratio is 7.4:2.6,the diffusion coefficient is the second highest.（3）A macroscopic manifestation of methane desorption is the amount of gas desorption from coal reservoirs.A machine learning model is established to achieve accurate prediction of gas desorption from tectonic coal reservoirs in order to improve the safety evaluation system of coal and gas prominence in tectonic coal reservoirs.