Research On Gas Migration In The Fissure Water Of Coal Seam

Part of the fissure water is contained in coal seam roof and floor rocks, when borehole communicate the coal seam roof and floor rocks, fissure water will go into the coal seam. In the process of gas extraction, gas goes forward under the pressure gradient in the coal seam fracture, what's more, gas diffuses under the concentration gradient in the coal fissure water. This way of migration of predecessor's research is less. This thesis studies the diffusion regularity of coal methane in saturated water, through the laboratory experiment and numerical simulation to analyze the effects of factors such as temperature, pressure, salinity and surfactant on methane diffusion.?1? Established the diffusion experiment of methane in the coal pore water, testing the change of the methane concentration in the chamber, drawing the curve of methane concentrations over time. Use the diffusion coefficient model to solve the diffusion coefficient of methane.?2? Diffusion concentration and diffusion coefficient decrease with the temperature. Temperature will speed up the methane molecule movement and reduce the methane concentration in water. Reduce the water viscosity and the diffusion resistance of methane in the water, promote the diffusion of methane. The greater the gas pressure is, the more gas molecules get into the water. The concentration of methane in the water will increase, the diffusion becomes much faster, the diffusion coefficient will rise. The results of simulation about methane diffusion under different temperature and pressure are consistent with the experimental results.?3? The diffusion concentration and coefficient of methane decrease with water salinity. The diffusion coefficient is negative correlation with the salinity. The water salinity will reduce degree of clearance and hydration molecule number, reduce methane molecular diffusion channel and carrier, thereby reducing the diffusion of methane in the water.?4? Methane diffusion concentration increase with the surfactant concentration, but incremental decrease. Methane diffusion coefficient in the water is positively correlation with surfactant concentration. Surfactants can reduce the water surface tension and surface free energy, then, methane concentration in the water and coefficient will increase.?5? The time of methane diffusion in coal fissure water is obvious long compared with diffusion in the pure water, the diffusion concentration and coefficient became low. Methane diffusion in coal pore is influenced by pore skeleton, porosity, and sinuosity. Diffusion coefficient increases with the porosity, the diffusion path increases with coal porosity, and the diffusion resistance is opposite. The greater porosity is, the faster methane diffusion is. The relationship between methane diffusion coefficient and porosity is shown below.De=0.93×10^-9·?^1.2...