School of Petroleum Engineering, China University of Petroleum, Qingdao, Shandong, 266580, China.
Sci Rep. 2016 Sep 2;6:32393. doi: 10.1038/srep32393.
To investigate the gas flow characteristics in tight porous media, a microscale lattice Boltzmann (LB) model with the regularization procedure is firstly adopted to simulate gas flow in three-dimensional (3D) digital rocks. A shale digital rock and a sandstone digital rock are reconstructed to study the effects of pressure, temperature and pore size on microscale gas flow. The simulation results show that because of the microscale effect in tight porous media, the apparent permeability is always higher than the intrinsic permeability, and with the decrease of pressure or pore size, or with the increase of temperature, the difference between apparent permeability and intrinsic permeability increases. In addition, the Knudsen numbers under different conditions are calculated and the results show that gas flow characteristics in the digital rocks under different Knudsen numbers are quite different. With the increase of Knudsen number, gas flow in the digital rocks becomes more uniform and the effect of heterogeneity of the porous media on gas flow decreases. Finally, two commonly used apparent permeability calculation models are evaluated by the simulation results and the Klinkenberg model shows better accuracy. In addition, a better proportionality factor in Klinkenberg model is proposed according to the simulation results.
为了研究致密多孔介质中的气体流动特性，首先采用带正则化过程的微尺度格子玻尔兹曼（LB）模型来模拟三维（3D）数字岩心中的气体流动。重建了页岩数字岩心和砂岩数字岩心，以研究压力、温度和孔径对微尺度气体流动的影响。模拟结果表明，由于致密多孔介质中的微尺度效应，表观渗透率始终高于本征渗透率，并且随着压力或孔径的减小，或随着温度的升高，表观渗透率与本征渗透率之间的差异增大。此外，计算了不同条件下的克努森数，结果表明，不同克努森数下数字岩心中的气体流动特征有很大的不同。随着克努森数的增加，数字岩心中的气体流动变得更加均匀，多孔介质的非均质性对气体流动的影响减小。最后，通过模拟结果评估了两种常用的表观渗透率计算模型，结果表明克林肯伯格模型具有更高的准确性。此外，根据模拟结果提出了克林肯伯格模型中更好的比例系数。
