The Experimental Research Of Characteristics And Influence Factors Of Pore Fracture Of High Rank By LNMR

The fracture characteristics of coal seams are the main factors affecting theoccurrence and migration of gas in coal seams,it is of great significance to study the characteristics of fractures in coal seams to study the occurrence and migration of gas in coal seam,to prevent and control gas accidents to evaluate and develop coaled methane.In this paper,a low field NMR technique with high accuracy,fast detectionspeed,simple sample preparation and no physical damage to the sample was employed to study on the development characteristics of primary pore fracture of high degree of metamorphism of coal.The high rank coal samples which is collected from different mine like NO.1 Mine of Zhaogu,NO.2 Mine of Zhaogu,Mount Jiuli coalmine and the Mine of WangTaipu was used to do the experiment of low field of NMR.Firstly,had studied on the characteristics of high rank coal pore fracture,and the fractal dimension of T₂ spectra of different coal samples was calculated.Secondly,had studied the influencing factors on the coal hole fractured by changing the confining pressure and respectively applied to coal high temperature?100??and low temperature?-209??and other methods.The conclusions are as follows:?The coal pore volume was in direct proportion to the V_dafaf of coal;the microspore and small hole of coal was developed,and the mesopore and large hole wasn't developed.With the increased of the proportion of microspore,the porosity,permeability and movable fluid saturation decreased;with the increased of small hole proportion,the porosity,permeability of coal sample and movable fluid saturation increased;High rank tiny pore has obvious fractal structure.?The confining pressure subjected to high rank coal samples has a certain effect on the pore fracture.With the increase of loading confining pressure,the pore volume of coal sample decreased,the porosity decreased gradually,damping as power function,the pore connectivity enhancemented in coal samples,the proportion of pores in coal samples increases,while the proportion of large pores decreases,the permeability has different trends.?The temperature has a certain effect on the pore fracture characteristics of high rank coal samples.After low temperature treatment of coal,the pore volume of it increased,and the porosity and permeability increased too.The proportion of microspores in coal samples is decreased,the proportion of small holes is increased,the proportion of mesopores is basically unchanged,and the proportion of large pores increases.After high temperature treatment of coal,the pore volume of it decreased,and the porosity and permeability decreased too.The proportion of microspores in coal samples is increased,the proportion of small holes is decreased,the proportion of mesopores is basically unchanged,and the proportion of large pores decreases.