水分子在微孔隙介质中的受限扩散模拟

在饱和多相流体孔隙介质中，利用核磁共振测得的扩散系数可以区分油气水，并用于饱和度等岩石物理参数的求取，但在微小孔隙（< 20 μm）中，流体的表观扩散系数会偏离其自由扩散系数．通过有限差分和随机游走模拟方法对水分子在单孔隙及多孔隙介质中的扩散进行数值模拟，考察水分子扩散受限的程度．结合核磁共振在测井及实验室岩石物理应用的技术，进一步分析了受限扩散对求取油水饱和度等岩石物理参数造成的影响．同时，分析总结了两种模拟方法的使用条件及优缺点．

Simulation of Restricted Diffusion of Water Molecules in Micropores

In petroleum exploration, diffusion coefficient measured with NMR techniques is often used to identify fluid types (e.g., oil, water, and gas) and to calculate the saturation degree of reservoir rocks. In the micro-pores, however, the apparent or effective diffusion coefficient must be lower than the free diffusion coefficient. In this paper, the relationship between pore size and apparent diffusion coefficient is simulated using the finite difference and random walk methods. The effects of restricted diffusion on the accuracy of the petrophysical parameter calculations were analyzed under the well-logging and laboratory
conditions. Lastly, the application conditions and advantages of the two simulation methods were discussed.