【作者】 张鹏；

【导师】 梁卫国；

【作者基本信息】 太原理工大学 ， 采矿工程， 2012， 硕士

【摘要】 煤层气是煤矿安全生产的主要危害,是造成温室效应与臭氧层破坏的主要气体,同时煤层气作为一种新型的洁净能源,可以改善我国以煤炭为主的不合理的能源结构。因此,从安全、环保和能源的角度看,煤层气的开采具有重要意义。本文针对我国煤层气藏低渗透、低饱和、低压力的特点和煤层气采收率低的现状,采用注入二氧化碳驱替的技术来提高煤层气的采收率。本文首先介绍了煤体孔裂隙结构特征、煤层气的赋存状态和运移产出机理以及煤层气的吸附解吸特征。然后在此基础上进行了甲烷、二氧化碳气体的渗透率测试试验,通过试验得出：煤体渗透率受体积应力及渗透压力的双重影响,渗透压一定时,随体积应力增大渗透率减小,主要由煤体的变形作用引起；体积应力一定时,随渗透压增大渗透率的变化不是单调的而是存在一个临界点,渗透压小于这一临界压力值时渗透率减小,渗透压大于这一临界压力值时,渗透率呈现逐渐增大的趋势,主要是由气体的吸附作用引起；并且二氧化碳的渗透率是甲烷渗透率的10倍以上。最后进行不同压力下甲烷和二氧化碳气体的吸附、甲烷解吸和注二氧化碳驱替甲烷等试验,实验结果显示,甲烷和二氧化碳吸附、解吸曲线基本相同,体积应力一定时渗透压增大吸附量也相应增大,相同压力下二氧化碳的吸附量远远大于甲烷的吸附量,渗透压分别为6MPa和7.5MPa时,煤层气解吸率分别为36.9%和37.2%,两种情况下甲烷的解吸率变化不大,由此可知煤体解吸量和渗透压力的大小几乎无关,而是与煤体本身含气量的多少有关；驱替压力6MPa时,注气开采率、瓦斯解吸率、注气开采增产率和置换比分别为71%、36.9%、34.1%和6.7,驱替压力7.5MPa时,相应的注气开采率、瓦斯解吸率、注气开采增产率和置换比分别为73%、37.2%、35.8%和6.1,驱替压力在一定程度上能够提高驱替效率,采用注二氧化碳气体驱替的技术可以使煤层气的产量提高大约35%,同时也使二氧化碳气体永久埋存于煤层中,减少了二氧化碳气体对环境的污染和瓦斯爆炸事故的发生。更多还原

【Abstract】 Methane is the main harm of the safety and production of coal mine, which was the main gas causing greenhouse-effect and damaging the ozone layer. Meanwhile, coal-bed methane can change the coal-dominant unreasonable energy structure.of the our country as a new type of clean energy. Therefore, the exploitation of coal-bed methane is important from the aspect of safety, environmental protection and energy.The characteristics of the CBM of our country are low permeability,low saturation, low pressure and low recovery rate of CBM. According to the these characteristics, the thesis focuses on the improving the mining rate through the technology, which use carbon dioxide to replace CBM. Firstly,the characteristics of coal hole fracturing structure, occurrence state of the CBM, mechanism of migration and outputting, and adsorptive and desorptive features of CBM are studied. Then, the author does a research about the permeability of the methane and carbon dioxide. Through the experiment it can be concluded that permeability of coal are affected by volume stress and osmotic pressure. When the osmotic pressure is quantitative, the volume stress increases and the osmotic pressure reduces, which are caused by the deformation of the coal. When the volume stress pressure is quantitative, permeability changes as the increase of osmotic pressure, which is not drab but has a critical point. When the osmotic pressure is below the critical point, permeability reduces. When the osmotic pressure is above the critical point, permeability increases. All of these are caused by the value of the gas absorption. Meanwhile,the permeability of carbon dioxide is ten times more than methane. Finally, the author does experiments about the absorption of carbon dioxide, desorption of methane and forcing methane out with the injection of carbon dioxide. The experiment shows that the absorption curve and desorption curve are same in some degree. When the volume stress pressure is quantitative, the absorption capacity increases according to the increase of osmotic pressure. Under the same pressure, the absorption capacity of carbon dioxide is much more than methane. Their osmotic pressures are6MPa and7.5MPa, and their CBA desorption rate are36.9%and37.2%. From the experiment, it is clear that the desorption rate of coal has no relation with osmotic pressure, but related closely to the air containing of itself. When the forcing pressures are6MPa and7.5MPa, the mining gas injection rates are71%and73%, the CBA desorption rates are36.9%and37.2%, the increasing rates of mining gas injection are34.1%and35.8%, and the replacement ratios are6.7and6.1. The forcing pressure can improve the forcing rate in some degree. So it is clear that the production of coalbed methane can increased by35%by this technology. Meanwhile it can also bury the carbon dioxide in the coal-bed forever, reduce the environmental pollution caused by carbon dioxide, and reduce the gas explosion accidents.更多还原