不同加压注水条件影响煤样渗透特性实验研究

发布时间：2018-10-31 10:41

【摘要】：在我国煤矿开采过程中,由于开采深度的增加,导致瓦斯含量升高,瓦斯压力变大,再加上我国的地质条件比较复杂,因此很多矿井都存在着瓦斯突出的危险。本文通过从煤的渗透率着手来解决瓦斯突出这一难题。影响煤样渗透率的因素特别多,包括地应力、温度、孔隙压力、含水率等方面,但是地应力、温度、孔隙压力这些方面到目前为止已经有很多学者做过研究,研究内容也已经比较完善。本文主要从煤样含水率、煤样变质程度、不同加压注水条件、添加表面活性剂这几个方面来展开研究。在分析国内外煤样渗透特性实验研究的基础上,基于自主研制的三轴渗透实验装置,采用江西省某矿区的无烟煤、山西某矿区的焦煤和河北某矿区的长焰煤为实验煤样,进行了不同条件下的煤样渗透特性实验,研究不同条件对煤样渗透特性的影响规律和机理。结合压汞实验测定煤样加压注水前后的孔隙分布特征以及不同压力注水后煤样孔隙变化特征,探讨煤层孔隙结构和渗透特性之间的关系。通过接触角测定仪测定纯水和表面活性剂的接触角、表面张力,进行表面活性剂的优选,通过接触角、表面张力计算毛细管力,分析添加表面活性剂对毛细管力的影响,进而对煤样渗透特性的影响。通过实验室实验以及理论分析,系统揭示其影响机理。实验结果表明:(1)对同种煤样进行不同含水率条件下的渗透率实验,随着含水率增大,煤样渗透率下降,并且在含水率较低时,煤体水分的增加对渗透率的影响更明显;对3种不同变质程度煤样的渗透率实验进行分析,可以看出煤样的变质程度越高,随着含水率的增加,渗透率的下降趋势越明显,下降幅度也越大;(2)对长焰煤煤样进行不同压力注水,随着注水压力的增加,煤样内部含水率逐渐增大,但是由于压力水会促使煤样内部孔隙孔径增大,导致毛细管力减小,最终渗透率的值还是增大;对于不同变质程度的煤样(无烟煤、焦煤、长焰煤),当注水压力增大时,3种煤样的渗透率都有所增大,只是增大幅度有些不同。通过压汞实验和扫描电镜实验,可以看出,本次试验中所用煤样的孔隙结构随着变质程度越高,大孔、裂隙越发育,煤样的渗透率也越大;(3)对干燥煤样、饱和水煤样、饱和F1煤样进行渗透率实验,发现干燥煤样渗透率大于饱和F1煤样渗透率大于饱和水煤样渗透率。
[Abstract]:In the process of coal mining in our country, because of the increase of mining depth, the gas content increases, the gas pressure becomes bigger, and the geological conditions of our country are more complex, so many mines have the danger of gas outburst. In this paper, the problem of gas outburst is solved from coal permeability. There are many factors that affect the permeability of coal samples, including ground stress, temperature, pore pressure, water cut and so on. But so far, many scholars have done research on such aspects as in-situ stress, temperature, pore pressure, etc. The research content has also been relatively perfect. In this paper, water cut of coal sample, metamorphic degree of coal sample, water injection condition under different pressure, adding surfactant are studied. Based on the analysis of the experimental study on the permeability characteristics of coal samples at home and abroad, the anthracite from a mining area in Jiangxi Province, the coke coal from a mining area in Shanxi province and the long flame coal from a mining area in Hebei province are used as experimental coal samples based on the triaxial permeation experimental device developed by ourselves. Experiments on the permeability characteristics of coal samples under different conditions were carried out to study the influence of different conditions on the permeability characteristics of coal samples. Combined with mercury injection experiment, the pore distribution characteristics of coal samples before and after pressurized water injection and the pore variation characteristics of coal samples after different pressure water injection were measured, and the relationship between pore structure and permeability characteristics of coal seam was discussed. The contact angle and surface tension of pure water and surfactant were determined by contact angle measuring instrument, the optimum selection of surfactant was carried out, the capillary force was calculated by contact angle and surface tension, and the effect of adding surfactant on capillary force was analyzed. And then the influence on the permeability characteristics of coal sample. Through laboratory experiments and theoretical analysis, the influence mechanism is systematically revealed. The experimental results show that: (1) with the increase of water content, the permeability of coal sample decreases with the increase of water content, and the increase of water content of coal body has more obvious effect on permeability when the water content is low; By analyzing the permeability experiments of three kinds of coal samples with different metamorphic degrees, it can be seen that the higher the metamorphic degree of coal samples is, the more obvious the decreasing trend of permeability is with the increase of water content, and the larger the decrease range is. (2) with the increase of injection pressure, the water cut in the coal sample increases gradually, but the capillary force decreases because the pressure water will increase the pore diameter of the coal sample. The value of final permeability still increases; For coal samples with different metamorphism (anthracite, coking coal, long flame coal), the permeability of the three coal samples increases with the increase of injection pressure, but the increase range is different. Through mercury injection experiment and SEM experiment, it can be seen that the higher the degree of metamorphism, the larger the pore structure and the bigger the fracture, the greater the permeability of coal sample. (3) the permeability of dry coal sample, saturated water coal sample and saturated F1 coal sample is tested. It is found that the permeability of dry coal sample is greater than that of saturated F1 coal sample.
【学位授予单位】：华北科技学院
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TD712

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