Joint numerical microscale simulations of multiphase flow and NMR relaxation behavior in porous media using Lattice Boltzmann methods
Joint numerical microscale simulations of multiphase flow and NMR relaxation behavior in porous media using Lattice Boltzmann methods
复制标题
使用格子玻尔兹曼方法对多孔介质中的多相流和 NMR 弛豫行为进行联合数值微尺度模拟
DOI：
10.1002/2013wr014684
复制
发表时间：
2014
影响因子：
5.4
通讯作者：
N. Klitzsch
中科院分区：
文献类型：
--
作者：
O. Mohnke;M. Stiebler;N. Klitzsch
核磁共振弛豫法是研究岩石和土壤迁移和储存特性的有效工具。然而，由于核磁共振信号和岩石中的这些性质之间没有唯一的关系，因此已经发表了各种从核磁共振弛豫数据推导水力学性质的经验模型。作为对实验室测量的补充，本文介绍了一个数值框架，用于在微米尺度上联合模拟NMR弛豫实验和两相流。在此，NMR扩散方程与计算流体动力学中使用的已建立的格子玻尔兹曼算法相关联。使用完全和部分水饱和的简单孔隙几何形状的解析解，对表面限制和扩散限制弛豫机制的数值模拟NMR数据进行了验证。随后，使用从疏松砂岩的三维计算机断层扫描（CT）数据中获得的复杂孔隙空间进行模拟，并将结果与相应的NMR T1弛豫数据进行比较。对于不同的水饱和度模拟的NMR瞬态匹配关于初始振幅的测量数据（即，孔隙度和饱和度）和松弛行为（即，水饱和孔隙的分布）。因此，我们提供了一个模拟工具，使结构和物理化学性质的影响，如孔隙连通性和孔隙耦合，表面弛豫率，或扩散，部分饱和多孔介质，如岩石或土壤，与NMR T1弛豫数据的研究。
Nuclear magnetic resonance (NMR) relaxometry is a useful tool to estimate transport and storage properties of rocks and soils. However, as there is no unique relation between the NMR signal and these properties in rocks, a variety of empirical models on deriving hydraulic properties from NMR relaxometry data have been published. Complementary to laboratory measurements, this paper introduces a numerical framework to jointly simulate NMR relaxometry experiments and two‐phase flow on the micrometer scale. Herein, the NMR diffusion equations were tied to an established Lattice Boltzmann algorithm used in computational fluid dynamics. The numerically simulated NMR data were validated for both surface‐limited and diffusion‐limited relaxation regimes using analytical solutions available for fully and partially water‐saturated simple pore geometries. Subsequently, simulations were compiled using a complex pore space derived from three‐dimensional computer tomography (CT) data of an unconsolidated sand and the results were compared to respective NMR T1 relaxometry data. The NMR transients simulated for different water saturations matched the measured data regarding initial amplitudes (i.e., porosity and saturation) and relaxation behavior (i.e., distribution of water‐saturated pores). Thus, we provide a simulation tool that enables study of the influences of structural and physicochemical properties, such as pore connectivity and pore coupling, surface relaxivity, or diffusivity, on partially saturated porous media, e.g, rocks or soils, with NMR T1 relaxometry data.