Experimental Study On Permeability-increasing By Fenton Modified Different Rank Coals

As an associated mineral resource of coal,CBM is an efficient and clean energy,and its efficient utilization will bring huge economic benefits.However,due to the complex geological conditions,coal reservoirs in China have the characteristics of high permeability,low permeability,easily absorbed and the coalbed gas has the characteristics of easy absorption and desorption.The traditional hydraulic stimulation technology is ineffective,so it is urgent to study the chemical modification technology of low permeability coal seam matching with hydraulic measures.In this paper,Fenton reagents were used to modify different grades and scales of coal.Desorption-percolation experiments were performed on the coal before and after treatment.After Fenton modification,the adsorption amount of coal sample is reduced,and the gas diffusion coefficient and permeability increase.Therefore,it can be seen that Fenton modification inhibits the adsorption of methane on coal and promotes desorption and diffusion ability of coal.At the same time,the percolation experiment of Fenton modified coal shows that the permeability of modified coal increases,the change trend of the desorption percolation characteristics of Fenton modification with different coal rank is more significant with the reduction of coal rank.The T₂ relaxation time spectrum of coal samples with different coal rank after Fenton reagent modification was obtained by low field nuclear magnetic resonance?NMR?experimen.The variation of pore characteristics of coal samples before and after Fenton modification was analyzed by T₂ relaxation time spectrum.The variation trend and types of the surface functional groups of the experimental coal samples before and after the modification was measured by infrared spectroscopy.The influence of Fenton modification on the microstructure of coal surface and the influence of the change of surface microstructure on desorption and diffusion characteristics are analyzed.The results show that Fenton modification can effectively promote the development of pore cracks in coal,meanwhile,makes the amount of oxygen-containing functional groups on the surface of coal increases and the adsorption capacity of coal on methane decreases,the ability of the diffusion and seepage of coal is improved,which provides a theoretical basis for the penetration of low permeability coal seams and the efficient extraction of gas.