瓦斯抽采钻孔有效影响半径的理论模型及数值分析

Theoretical Model and Numerical Analysis for the Effective Influence Radius of Gas Drainage Borehole

基于现场测定瓦斯抽采有效影响半径的工作周期长、工程量大、实施成本高且成功率低的弊端,建立了考虑瓦斯孔隙压力和吸附膨胀应力作用下含瓦斯煤岩体的固-气耦合运移方程,同时提出以临界瓦斯压力pc和临界瓦斯含量wc联合确定有效影响半径的准则,克服了传统单一指标下有效影响半径估计时经常偏大的问题。采用该理论模型可以计算不同预抽期内,煤层瓦斯压力、瓦斯含量和瓦斯预抽率等动态渗流参数的变化,并基于计算结果揭示了瓦斯抽采有效影响半径与预抽时间成正指数函数的关系,可以方便地确定不同预抽期内瓦斯抽采钻孔的有效影响半径,为钻孔参数的合理设计和布置提供了理论参考依据。

In this paper, the author established gas-solid coupled transport equations of the gassy coal-rock, with the consideration of gas pore pressure and gas sorption-induced stress, and also proposed a new criteria to confirm the effective influence radius by connecting critical gas pressure Pc and critical gas content we. It improved the problem of higher estimation for the effective influence radius, which is caused by traditional single index method. Many dynamic percolation parameters can be calculated at different pre-pumping period by this theoretical model, such as coal gas pressure, gas content, gas pre-pumping rate, and so on. According to the calculation results, a positively exponential interrelationship is revealed between the effective influence radius of gas drainage and the pre-pumping period, which can be used to confirm the effective influence radius of gas drainage at different pre-pumping period, and furthermore, to provide a theoretical reference for the rational designs and layout of the borehole.