Research on determination method of effective drainage radius of gas drainage borehole
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摘要: 针对现有瓦斯抽采钻孔有效抽采半径测定方法存在测定工艺复杂且准确性较低的问题,提出了以抽采钻孔瓦斯流量负指数衰减规律为基础、以工作面抽采达标指标为判据的有效抽采半径测定方法,推导出了以抽采率表示的钻孔有效抽采半径计算公式。通过测定煤层的抽采钻孔瓦斯流量衰减规律得到百米钻孔瓦斯初始抽采量和抽采钻孔瓦斯涌出衰减系数,结合工作面抽采达标判据,依据抽采率确定煤层在不同抽采时间所对应的钻孔有效抽采半径:当工作面瓦斯涌出量主要来自于邻近层及围岩时,以工作面的绝对瓦斯涌出量为判据确定工作面瓦斯抽采率,进而计算有效抽采半径;当工作面瓦斯涌出量主要来自于本煤层时,以设计抽采率和可解吸瓦斯量为指标进行有效抽采半径的计算;当开采突出煤层时,工作面原始瓦斯压力大于0.74 MPa或原始瓦斯含量大于8 m3/t时,以原始瓦斯压力或原始瓦斯含量计算工作面瓦斯抽采率,进而计算有效抽采半径。现场测试结果验证了该方法的正确性。Abstract: In order to solve the problems of complex process and lower accuracy in current determination method of effective drainage radius of gas drainage borehole, a determination method of effective drainage radius was put forward, which is based on the law of negative exponential attenuation of gas flow in boreholes and taking the index of gas extraction standard on working face as criterion.The calculation formula of effective drainage radius of boreholes in terms of drainage rate was derived. The initial gas drainage volume and gas emission attenuation coefficient of hundreds of meters borehole are obtained by measuring the attenuation law of gas flow in the coal seam, combined with the criterion of gas extraction standard on working face, the effective drainage radius of borehole corresponding to different drainage time of coal seam is determined according to the drainage rate: when the gas emission amount of the working face mainly comes from the adjacent strata and surrounding rock, the absolute gas emission of working face is taken as the criterion to determine the gas drainage rate of the working face, and then the effective drainage radius is calculated; when the gas emission amount of the working face mainly comes from the coal seam, the effective drainage radius is calculated with the design drainage rate and the desorption gas quantity as the index; when the outburst coal seam is mined, the original gas pressure of the working face is greater than 0.74 MPa or the original gas content is greater than 8 m3/t, the gas drainage rate is calculated by measuring the original gas pressure or the original gas content, and then the effective drainage radius is calculated. The field test results verify the correctness of the method.
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Key words:
- gas drainage /
- drainage borehole /
- effective drainage radius /
- gas drainage rate /
- residual gas content
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