Experimental Study And Microscropic Mechanism On Inhibiting Effect For Gas Desorption Through Water Injection

Based on consulting a large number of relevant materials, In view of the previous study of moisture effect on gas desorption laws more focused on atmospheric water, it cannot simulate the conditions of coal seam water injection well, and more focused on description of macro phenomenon, the microscopic mechanism of its existence cannot be deeply researched, this paper uses the independently researched and developed high-pressure water injection coal bed methane(CBM) isothermal desorption experiment table, mainly to study the influence of the high pressure water injection to coal sample methane desorption characteristics and microcosmic influence mechanism. Through the theoretical analysis of prevention and control gas by coal seam water injection, law of coal bed gas adsorption and desorption, and influence of the moisture to gas desorption characteristics.First of all, we made an introduction to the composition and function of laboratory equipment, determined the coal sample basic parameters of the high, medium and low three different metamorphic degree, selected the five basic surfactant to make up the surfactant solution of different proportion. Based on the measurement of contact Angle and surface tension of solution, a surfactant solution was selected that has a best wetting effect for application. Then respectively we carried some contrast experiments of coal sample gas desorption under the condition of same water injection pressure and different adsorption equilibrium pressure, different water injection pressure and same adsorption equilibrium pressure, injecting pure water or surfactant solution, different metamophic degree of coal sample and same condition of water injection. According to the statistical results of cumulative gas desorption quantity and desorption speed under the condition of different pressure water injection, the influence of gas desorption laws on the experimental conditions of the water pressure was analyzed.Then the fitting analysis about above experimental data by the seven desorption experience formula from past a lot of study and error comparison analysis of calculated value by the empirical formula and measured value were made. Finally, Ustinov type is the best fitting formula that described the influence of the high pressure water injection to coal sample methane desorption law.At the same time, with the help of mercury injection experiment and scanning mirror respectively, the pore characteristics parameters of coal samples under the conditions of different pressure water injection and drying are measured and the micro pore characteristics of coal sample are observed, combining with macroscopic experimental phenomena, the influence mechanism of coal sample gas desorption law was obtained by comparative analysis under the conditions of different pressure water injection. In addition, combining the theory of micro-view such as pore size, it analyzed how the change of porosity characteristics of high pressure water injection of coal sample affects macro total desorption quantity and desorption rate, and it is concluded that water injection in coal seam has a inhibition effect for gas desorption.Finally, through the analysis of the theoretical and practical significance of the experiment, the experimental results for coal seam water injection to the prevention and control of gas is of great significance. With the economic and equipment conditions allowed, as far as possible improving water injection pressure and in the process of coal seam water injection adding the surfactant solution whose contact Angle and surface tension is as small as possible can effectively reduce the gas radiation initial velocity and release quantity for the prevention and control of gas disaster in coal mine has an important theoretical and practical significance.