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钻孔钻进期间瓦斯涌出数值模拟

Numerical simulation of gas emission during borehole drilling

  • 摘要: 为了分析钻孔钻进瓦斯涌出规律,建立流—固耦合双孔介质模型,并模拟分析了瓦斯压力、孔径、基质解吸时间及Klinkenberg因子对钻孔钻进瓦斯涌出的影响。结果表明,不同位置孔壁暴露时间不同,压力降幅不等,瓦斯渗流速度不同;瓦斯流量呈现增长趋势,且增长速度不断减缓,使用单孔模型则会严重高估瓦斯流量。瓦斯压力是影响钻进瓦斯涌出的关键性因素;孔径增大促使瓦斯流量及涌出量增高;基质瓦斯解吸时间增大减少了对裂隙瓦斯的补充;Klinkenberg因子能够显著促进渗透率的增大进而提高渗流速度,增大瓦斯涌出量,但瓦斯涌出量存在一个极限值。

     

    Abstract: In order to analyze gas emission during borehole drilling, a model of fluid-solid coupling dual-hole media was established, and the effects of gas pressure, borehole diameter, matrix desorption time and Klinkenberg factor on gas emission during borehole drilling were simulated and analyzed. The results show that the exposure time, pressure drop and gas seepage rate are different at different positions of hole wall. The gas flow shows a growing trend and the growth rate keeps slowing down, and using a single-hole model will seriously overestimate gas flow. The gas pressure is the key factor affecting gas emission in drilling; the increase of hole diameter promotes the increase of gas flow and emission; the increase of matrix gas desorption time reduces the gas replenishment to the fracture; Klinkenberg factor can significantly promote the increase of permeability, thereby increasing the seepage speed and increasing the amount of gas emission, but there is a limit value of gas emission.

     

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