声场作用下煤层气渗流特性的研究

发布时间：2018-09-12 07:50

【摘要】：我国煤层气资源丰富,煤层气是近二十年世界上崛起的一种优质高效洁净的新能源,另一方面,煤层气又是煤矿重大灾害事故的有害源,在当前能源紧张的局势下,加快煤层气的开发利用,对改善我国能源结构、能源的充分利用、安全生产和减少环境污染等具有重要现实意义。论文基于声场提高煤层气抽采率的方法,采用室内试验、理论分析、数值模拟、现场试验研究,开展了声场作用前后煤体微观结构、声波在煤体多孔介质中传播规律、声场作用下煤层气渗流特性、声场提高煤层气抽采率的现场试验研究,研究取得的主要成果有:声场作用后,煤体的孔隙结构变化趋势表现为“整体增大,离散性增强,两段式波动变化”的特征,表明声场作用改变了煤体的原生孔隙结构,增大了煤体的孔隙度、孔容和比表面积,增加了煤体的裂隙率、连通率。不加声场和加声场两种条件下煤中甲烷渗流规律基本一致,随着有效应力增加,煤层渗透率呈负指数函数递减。声场作用下煤体渗透率大于不加声场,且煤样渗透率随声场强度线性增大,随作用时间的增加而增大,表明声场能提高煤体渗透率。声场作用能减缓应力对煤体渗透率的伤害,提高煤体的渗透能力,声场作用后煤体渗透率对应力更敏感,高频率声场作用下的应力敏感性系数高于低频率声场作用,因此在煤层气抽采过程中,宜采用低频高能的换能器。数值分析与现场试验结果表明,煤体的渗透率与应力、温度、孔隙压力和声场作用密切相关,离声场震源越近,作用效果越明显,离声场震源越远,瓦斯流量衰减呈负指数函数关系。以上研究成果丰富并创新煤层气高效开采理论,对高效抽采煤层气、减少煤矿瓦斯事故具有重要的科学意义和实用价值。
[Abstract]:Our country is rich in coal bed methane resources, coal bed methane is a kind of high quality, high efficiency and clean new energy rising in the world in the last two decades. On the other hand, coal bed methane is also the harmful source of coal mine major disaster accident. Speeding up the development and utilization of CBM is of great practical significance in improving the energy structure, making full use of energy, safe production and reducing environmental pollution in China. Based on the method of improving the extraction rate of coalbed methane by sound field, laboratory test, theoretical analysis, numerical simulation and field test are used to study the microstructure of coal body before and after the action of sound field, and the propagation law of sound wave in porous medium of coal body. Under the action of sound field, the percolation characteristics of coalbed methane and the field test study of improving the extraction rate of coalbed methane by sound field are studied. The main results obtained from the study are as follows: after the action of sound field, the change tendency of pore structure of coal body is: "the whole increases, the dispersion increases," The characteristics of two-stage fluctuation show that the acoustic field changes the primary pore structure of the coal body, increases the porosity, pore volume and specific surface area of the coal body, and increases the fracture rate and connectivity of the coal body. The law of methane percolation in coal is basically the same under the condition of no sound field and no sound field. With the increase of effective stress, the permeability of coal seam decreases with negative exponential function. Under the action of sound field, the permeability of coal body is larger than that of unsound field, and the permeability of coal sample increases linearly with the intensity of sound field and increases with the increase of action time, which indicates that the sound field can increase the permeability of coal body. The effect of sound field can reduce the damage of stress to the permeability of coal and improve the permeability of coal. The permeability of coal is more sensitive to stress after the action of sound field, and the sensitivity coefficient of stress under the action of high frequency sound field is higher than that of low frequency sound field. Therefore, the low frequency and high energy transducer should be used in the process of coal bed methane extraction. The results of numerical analysis and field test show that the permeability of coal is closely related to stress, temperature, pore pressure and sound field, and the closer it is to the source of sound field, the more obvious the effect is and the farther away from the source of sound field. The attenuation of gas discharge is a negative exponential function. The above research results enrich and innovate the theory of high efficiency mining of coalbed methane, which is of great scientific significance and practical value for the efficient extraction of coalbed methane and the reduction of coal mine gas accidents.
【学位授予单位】：重庆大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TE312

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