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煤层气在煤岩裂隙中流动时,由于其粘度系数较小,很容易产生非Darcy现象。因此,考虑煤层气的非Darcy渗流将会使得研究结果更加客观和准确,对煤层气开采具有实际意义。首先将实物裂隙高清拍照导入Matlab软件中进行图像二值化处理,再利用COMSOL软件对二值图像进行模型重构和数值模拟。模拟结果显示,煤层气渗流速度随着裂隙尺度的变化而不断改变,速度随时间不断增加,但区域渗流速度分布状态保持不变。与Darcy结果的对比分析可知,相同压力梯度下,考虑非Darcy因素的产气量要明显小于仅考虑Darcy因素的情况。同时,结果显示,在渗透率不同的煤裂隙中,煤层气的渗流速度不同。渗透率较大时,渗流速度相对较大,同样,渗透率较小时,渗透速度较小。
When CBM flows in coal and rock fracture, it is easy to produce non-Darcy phenomenon due to its low viscosity coefficient. Therefore, considering the non-Darcy seepage of CBM will make the research result more objective and accurate, which is of practical significance to the exploitation of CBM. Firstly, the real fractured high-definition camera was imported into Matlab software for image binarization, and the binary image was reconstructed and simulated by COMSOL software. The simulation results show that the seepage velocity of coalbed methane changes continuously with the change of the fracture scale, and the velocity increases with time, but the velocity of the seepage velocity in the area remains the same. Comparing with Darcy’s result, we can see that under the same pressure gradient, the gas production considering non-Darcy factor is obviously less than the Darcy factor only. Meanwhile, the results show that CBM seepage velocity is different in coal fractures with different permeability. When the permeability is large, the seepage velocity is relatively large. Similarly, when the permeability is small, the seepage velocity is smaller.