Research And Application Of Permecbility Technology With CO₂ Phase Transformation In Guizhou Soft And Low Permeability Coal Seam

Guizhou has rich reserves of coal resources,and the geological structure of the coal mining area is complex and varied,with typical mountainous regions.coal seams have many layers,low permeability,and coal mine safety situation are still severe.CO₂fracturing antireflection and desorption technology uses the high-pressure wave generated when liquid CO₂ is converted into a gas state as a power source.Through the high pressure blasting,the pore structure characteristics of the coal matrix are changed,Using the“competitive adsorption”and“displacement adsorption”between CO₂ and CH₄,CO₂ flooding is achieved and CH₄ is released to decompress large areas of coal.In this paper,the difficulties of gas drainage and recovery in low gas permeability coal seams in Guizhou are solved.Theoretical analysis of the crack and phase characteristics of CO₂ fracturing and anti-reflection technology is used.An algorithm for CO₂ fracturing and TNT energy conversion was written in the programming language.The crack of CO₂ fracturing and cracking in coal seams were numerically simulated,the CO₂ fracturing and antireflection technology in coal seams increased pressure relief.Through systematic research on the gas geology and gas drainage status of the Lvtang Coal Mine in Dafang County,Guizhou Province,CO₂ fracturing and anti-reflection technology test plan was developed at the return air lane of the S204 working face in the South Second Mining Area of the mine.Industrial testing.The test has achieved the following results:1.The concentration in the test borehole was increased from 21.22%to about60.91%,which was three times higher.More than 50%of the days after fracturing concentration is 85%of the total.The single-hole gas drainage volume increased from0.0426 m³/min before the test to 0.123-0.284 m³/min or more,increase of 3-5 times.2.The permeability coefficient of the coal seam in the fracturing zone is increased from 0.059 m²/(MPa².d^-1)to 0.442 m²/(MPa².d^-1),CO₂ fracturing and anti-reflection technology The air permeability coefficient of the body is increased by about 8 times.the attenuation coefficient of gas decreased by 53.6%.