Department of Earth Science and Engineering, Imperial College London, United Kingdom.
Phys Rev Lett. 2011 Nov 11;107(20):204502. doi: 10.1103/PhysRevLett.107.204502. Epub 2011 Nov 8.
We simulate transport of a solute through three-dimensional images of different rock samples, with resolutions of a few microns, representing geological media of increasing pore-scale complexity: a sandpack, a Berea sandstone, and a Portland limestone. We predict the propagators (concentration as a function of distance) measured on similar cores in nuclear magnetic resonance experiments and the dispersion coefficient as a function of Péclet number and time. The behavior is explained using continuous time random walks with a truncated power-law distribution of travel times: transport is qualitatively different for the complex limestone compared to the sandstone or sandpack, with long tailing, an almost immobile peak concentration, and a very slow approach to asymptotic dispersion.
我们通过三维图像模拟溶质在不同岩样中的传输，这些岩样的分辨率为几微米，代表着具有不同孔隙尺度复杂性的地质介质：一个沙箱、一个 Berea 砂岩和一个 Portland 石灰岩。我们预测了在类似核磁共振实验中测量的类似岩芯中的传播子（浓度作为距离的函数）和弥散系数作为 Peclet 数和时间的函数。使用截断幂律旅行时间分布的连续时间随机行走来解释这种行为：与砂岩或沙箱相比，复杂石灰岩的传输行为明显不同，具有长尾、几乎不可移动的峰值浓度和非常缓慢的渐近弥散。
