马兰矿煤体渗流特性及超长钻孔瓦斯抽采数值模拟研究

发布时间：2018-05-19 10:31

本文选题：渗流特性 + 数值模拟　；参考：《太原理工大学》2016年硕士论文

【摘要】：瓦斯涌出量高、治理难度大是多年来高瓦斯矿井安全生产面临的最关键的问题之一,高效的抽采瓦斯是解决该问题的主要方法。马兰矿多年来连续被鉴定为高瓦斯矿井,自2013年开始被鉴定为突出矿井,煤层瓦斯抽采工作从未间断,为了能够更加高效地进行瓦斯抽采,本文针对9#层的具体情况,采用实验的方法对本层煤的瓦斯渗流特性进行了多方面的研究,并将研究所得的渗透率的变化规律作为耦合变量引入到数值模拟所用的数学模型中,对本层煤使用超长钻孔进行煤层瓦斯抽采过程中瓦斯压力分布规律以及瓦斯抽采总量的变化进行了数值模拟,通过工程实践结果验证了数值模拟的正确性,并据此提出了下一步瓦斯抽采目标,具体研究内容如下:使用电液伺服三轴渗流实验装置研究了固定载荷下瓦斯压力、围压、轴向应力对含瓦斯煤渗透率的影响以及全应力-应变和卸围压条件下煤样渗透率变化规律。对实验结果进行分析得出:由于Klinkenberg效应的存在,瓦斯压力与渗透率之间存在明显的抛物线关系,Klinkenberg拐点在1.4MPa左右,低于1.4MPa时,渗透率逐渐降低,高于1.4MPa时,渗透率逐渐升高;围压和轴向应力与渗透率的变化关系都为非线性指数关系;含瓦斯煤全应力-应变以及卸围压过程中渗透率都表现出先减小后增大的规律,瓦斯压力较小时,轴向应力为整个破坏过程中最关键的因素,瓦斯压力越高,煤样越容易破碎,较大的瓦斯压力会在煤样破碎过程中起到决定性作用。使用COMSOL Multiphysics软件对瓦斯抽采钻孔深度不同、抽采负压不同、抽采时间不同时瓦斯压力分布规律和抽采瓦斯总量进行了数值模拟。模拟结果显示:抽采初期,钻孔浅处径向压力梯度的改变明显快于钻孔深处,随着抽采天数的增加,钻孔深处径向瓦斯压力梯度的稳定明显滞后与钻孔浅处,说明瓦斯抽采初期,瓦斯抽采重点区域在径向距离较小以及钻孔较浅区域,随着抽采天数的增加,瓦斯抽采重点区域向径向距离较大以及钻孔深处转移;钻孔深度越大,瓦斯抽采难度越大,适当提高瓦斯抽采负压能够有效提高钻孔深处瓦斯抽采效率;抽采负压为13KPa,钻孔总深度分别为600m、700m时,从抽采瓦斯总量可判断出其抽采瓦斯有效天数分别为为500d左右和600d左右;对马兰矿9#层600m超长钻孔进行了统计分析,通过对不同时期瓦斯抽采总量的分析验证了数值模拟的正确性,并据数值模拟提出,1#钻场有效抽采瓦斯时间为500d左右,单孔瓦斯抽采总量预计为105572m3,2#钻场有效抽采时间为600d左右,单孔瓦斯抽采总量预计为123167m3。通过本文的研究对9#层煤的瓦斯渗流特性以及抽采特点有了更加明确的认识,为今后对煤层瓦斯进行高效抽采提供了理论指导。
[Abstract]:The high quantity of gas emission and the difficulty of controlling gas are one of the most critical problems in the safe production of high gas mine for many years. The main method to solve this problem is to draw gas efficiently. Ma Lan Mine has been continuously identified as a high gas mine for many years, and has been identified as a outburst mine since 2013. In order to be more efficient in gas extraction, this paper aims at specific conditions of 9# layers. In this paper, the gas seepage characteristics of the coal bed are studied in many aspects by using the experimental method, and the law of the permeability variation obtained is introduced into the mathematical model used in the numerical simulation as a coupling variable. In this paper, the distribution law of gas pressure and the change of total amount of gas drainage in coal seam are numerically simulated by using super-long boreholes, and the correctness of the numerical simulation is verified by the engineering practice results. Based on this, the next target of gas extraction is put forward. The specific research contents are as follows: the gas pressure and confining pressure under fixed load are studied by using the electro-hydraulic servo triaxial seepage experimental device. The influence of axial stress on the permeability of gas-bearing coal and the variation of coal sample permeability under the conditions of total stress-strain and unloading confining pressure. The experimental results are as follows: due to the existence of Klinkenberg effect, there is an obvious parabola relationship between gas pressure and permeability. When the inflection point of Klinkenberg is about 1.4MPa, when it is lower than 1.4MPa, the permeability decreases gradually, and when it is higher than 1.4MPa, the permeability increases gradually. The variation of confining pressure, axial stress and permeability are all nonlinear exponential relations, the total stress-strain of gas-bearing coal and permeability in the process of unloading confining pressure all show the law of decreasing first and then increasing, and the gas pressure is small. Axial stress is the most important factor in the whole failure process. The higher the gas pressure, the easier the coal sample to break, and the greater the gas pressure will play a decisive role in the coal sample crushing process. Numerical simulation was carried out by using COMSOL Multiphysics software to simulate the distribution law of gas pressure and the total amount of gas extraction at the same time, such as the different drilling depth, the different negative pressure, the different extraction time and the different borehole depth of gas extraction. The simulation results show that in the early stage of drainage, the radial pressure gradient of shallow borehole changes faster than that of deep hole, and with the increase of drainage days, the stability of radial pressure gradient of borehole is obviously lagged behind that of shallow borehole. It shows that in the early stage of gas extraction, the key area of gas extraction is smaller in radial distance and shallow in borehole. With the increase of days of gas extraction, the key area of gas drainage moves to the radial distance and the depth of borehole, the deeper the borehole is, the greater the borehole depth is. The greater the difficulty of gas extraction, the better the efficiency of gas extraction can be improved by properly increasing the negative pressure of gas extraction, when the negative pressure of extraction is 13kPaand the total depth of borehole is 600m / 700m, respectively. From the total amount of gas extraction, the effective days of gas extraction are about 500d and 600d respectively, and the statistical analysis of 600m super-long borehole in 9# layer of Ma Lan mine is carried out. The validity of the numerical simulation is verified by the analysis of the total amount of gas drainage in different periods. According to the numerical simulation, the effective gas extraction time is about 500 d in the drilling field of the Qia1# drill field, and the total amount of the gas drainage in the single hole is estimated to be about 600 d in the drilling field of 105572 m ~ 32#. The total amount of single hole gas drainage is estimated to be 123167m3. Through the research of this paper, the characteristics of gas percolation and extraction of 9# seam coal are more clearly understood, which provides theoretical guidance for the high efficiency gas drainage of coal seam in the future.
【学位授予单位】：太原理工大学
【学位级别】：硕士
【学位授予年份】：2016
【分类号】：TD712.6

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