基于CT三维重建的煤层气非达西渗流数值模拟

为了探究煤层气非达西渗流中各参数对渗流的影响，通过CT三维重建技术，建立了从现场采集到的6种煤样的真实模型。基于建立的真实模型，进行了在30种不同压力梯度下的煤层气渗流数值模拟试验。模拟试验结果表明：（1）在微观尺度下(<100 μm)，模拟得到的渗流速度与压力梯度符合Forchheimer高速非线性渗流规律；（2）渗透率随有效孔隙率的增长并不是绝对的，在有效孔隙率较大时会出现局部波折的情况，在相同压力梯度下，渗流速度总的趋势随有效孔隙率、渗透率、非达西系数的增大而增大；（3）非达西系数随着有效孔隙率和渗透率的增大而减小。幂函数拟合和多元回归分析结果表明有效孔隙率对非达西系数的影响最为显著，仅考虑有效孔隙率的经验公式可更加精确的估算非达西系数。由数值模拟结果得到的非达西经验常数为0.003 171，有效孔隙率幂次为-5.387 45。

Numerical simulation on non-Darcy seepage of CBM by means of 3D reconstruction based on computed tomography

In order to study the influence of parameters on the CBM non-Darcy flow,six real models of various coal samples collected from underground mine were created by 3D reconstruction based on computed tomography.The CBM non-Darcy flow was numerically simulated under 30 different pressure gradients based on the six real models.According to the simulation results,some conclusions can be drawn as follows:(1) At the micro-scale (<100 μm),the relationship between the seepage velocity and the pressure gradient is consistent with the Forchheimer high speed non-linear percolation rule；(2) Effective porosity and permeability are positively related,but in the case of larger porosity,local twists and turns occur.Under the same pressure gradient,the seepage velocity increases with the effective porosity,permeability,non-Darcy coefficient increase in a general trend；(3) The non-Darcy coefficient decreases with the increase of effective porosity and permeability.Analysis results obtained by power function fitting and multivariate regression show that the effective porosity is the most significant factor on the non-Darcy coefficient,only consideration on the influence of the effective porosity can be more accurate to estimate the non-Darcy coefficient.Through the calculation by the numerical simulation of non-Darcy,empirical constant is 0.003 171,the power of effective porosity is -5.387 45.