Experimental Research On The Technology Of Vibrating Increases Permeability In Gas-containing Coal

The coal gas reserves of China is large, the permeability of coal gas reservoir is low, the exploitation and using level of coal gas is in a small degree, and the coal gas disasters and accidents could be seen frequently. We can't directly find out the coal gas rich region in the outburst coal seam with geophysical exploration methods, but we can find out the related Geological structure with geophysical exploration methods,and thus find out the position of the coal gas rich region. Yet,we could only find out the coal gas rich region which has a high gas content with geophysical exploration methods. These geophysical exploration methods can't be used in gas extraction process.So, we should improve the permeability of coal seam, study on the theory of finding a more effective coal gas exploration method and find out measures to improve the methane production of low permeability coal bed.It has very important practical significance in improving coal gas exploration and coal mine safety in production.With the principle that high frequency vibration field could influence the characteristics of gas seepage and desorption,the author designed a vibration system that could supply high frequency vibration field and improve the quantity of gas desorption and change the permeability of coal mass. This vibration system make the high frequency vibration motor as the core, and it consists of the excitation system, circulation water cooling system, energy transfer system, absorption and desorption test system, compression system, gas supply system, data acquisition system, etc.This paper mainly introduce the influence of the vibration system to the permeability and of coal mass and the quantity of gas desorption. It has simulated the compaction of coal samples, the migration of coalbed gas, coal and gas outburst and the changes of permeability and microcosmic structure in different vibration condition.we have disscussed the gas desorption characteristics in the condition of different frequency, amplitude and vibration time.This paper researched the coal gas adsorption and desorption process and the changes of permeability in the vibration field.A set of large-scale simulation system is developed to simulate the action of gas adsorption and desorption under the vibration field. The corresponding total pressure, gas pressure, the effective stress, gas emission speed, coal temperature, times consumed, and vibration parameters were recorded and analyzed. Experimental results show that:In the process of gas desorption, total stress and gas pressure decreases with time in accordance with the law of exponent, gas emission speed decreases with time according to the logarithmic law. In the process of coal gas relief, the unloading effect or stress releasing effect in the high stress area are stronger than that in low stress area,and there is a rising in desorption speed in the initial desorption process. High frequency waves produced dynamic effect to increases coal mass and coal gas molecular energy and promotes gas desorption and migration. In the process of sound propagation, part of the energy converted into heat. The free gas volume swelled and coal gas pressure increased, and gas desorption and migration is promoted.Besides,experimental result also shows that under the action of high-frequency vibration field,a significant increase in the amount of methane desorption has been seen and the permeability has also increased significantly.The goal of increasing the permeability and desorption quantity could be achieved by the vibration to the gas-containing coal. With the increase of gas injection pressure, the permeability K is dropping, and the downtrend of K is more obvious after the vibration.In the process of gas free desorption, the slope of the curve to the gas free desorption quantity and time reduces gradually, and gradually tends to be a stable value.In each vibration desorption process, the desorption speed reduces quickly, but there is an obvious process that the free desorption speed firstly increase and then reduce in the initial desorption stage.Also we could find the same phenomenon of desorption speed in the experiments of vibration promoting gas desorption.Figure 41 table 9 reference 60...